Multispectral Quantum Dots-in-a-Well Infrared Detectors Using Plasmon Assisted Cavities

We present the design, fabrication, and characterization, of multi-spectral quantum dots-in-a-well (DWELL) infrared detectors, by the integration of a surface plasmon assisted resonant cavity with the infrared detector. A square lattice and rectangular lattice cavity, formed by modifying the square lattice have been used in this design. By confining the resonant mode of the cavity to detector active region, the detector responsivity and detectivity have been improved by a factor of 5. A spectral tuning of 5.5 to 7.2 μm has been observed in the peak response of the detectors, by tuning the lattice constant of the cavity. Simulations indicate the presence of two modes of absorption, which have been experimentally verified. The use of a rectangular lattice predicts highly polarization sensitive modes in x- and y-direction, which are observed in fabricated detectors. A peak detectivity of 3.1 x 10^9 cm √(Hz)/W was measured at 77 K. This design offers a cost-effective and simple method of encoding spectral and polarization information, in infrared focal plane arrays

Terahertz and mid-infrared photodetectors based on intersubband transitions in novel materials systems

The terahertz (THz) and mid-infrared (MIR) spectral regions have many potential applications in the industrial, biomedical, and military sectors. Yet, a wide portion of this region of the electromagnetic spectrum (particularly the THz range) is still relatively unexplored, due mainly to the absence of suitable sources and photodetectors, related to the lack of practical semiconductor materials with adequately small band gap energies. Intersubband transitions (ISBTs) between quantized energy states in quantum heterostructures provide tunable wavelengths over a broad spectral range including the THz region, by choosing appropriate layer thicknesses and compositions. This work focuses on the development of THz and MIR Quantum Well Infrared Photodetectors (QWIPs) based on ISBTs in GaN/AlGaN and Si/SiGe heterostructures. Due to their large optical phonon energies, GaN materials allow extending the spectral reach of existing far-infrared photodetectors based on GaAs, and may enable higher-temperature operation. In the area of MIR optoelectronic devices, I have focused on developing QWIPs based on ISBTs in Si/SiGe heterostructures in the form of on strain-engineered nanomembranes. Due to their non-polar nature, these materials are free from reststrahlen absorption and ultrafast resonant electron/phonon scattering, unlike traditional III-V semiconductors. Therefore, Si/SiGe quantum wells (QWs) are also promising candidates for high-temperature high-performance ISB device operation (particularly in the THz region), with the additional advantage of direct integration with CMOS technology. In this thesis work, numerical modeling is used to design the active region of the proposed devices, followed by sample fabrication and characterization based on lock-in step-scan Fourier transform infrared spectroscopy. Three specific QWIP devices have been developed. The first is a III-nitride THz QWIP based on a novel double-step QW design in order to alleviate the material limitations provided by the intrinsic electric fields of GaN/AlGaN heterostructures. Next, I have developed a THz GaN/AlGaN QWIP grown on semi-polar (202 ̅1 ̅) GaN, where the detrimental effects of the internal fields are almost completely eliminated. Finally, I have demonstrated a Si/SiGe MIR QWIP based on a novel fabrication approach, where nanomembrane strain engineering is used to address the materials quality issues normally found in SiGe QWs. Promising photodetector performance is obtained in all cases.2017-06-21T00:00:00

Multispectral plasmon enhanced quantum dots in a well infrared photodetectors

Infrared detectors in 3-5 μm and 8-12 μm regions are extensively used for applications in remote sensing, target detection and medical diagnostics. Detectors using intersubband transitions in the quantum dots in a well (DWELL) system for infrared detection have gained prominence recently, owing to their ability to detect normally incident light, bicolor detection and use of mature III-V technology. In this dissertation, two aspects of DWELL detectors that make them suitable for third generation infrared systems are discussed: 1) High temperature operation, 2) Multispectral detection. There are two parts to this dissertation. In the first part, an alternate structure with an improved operating temperature and thicker active region is presented. Traditionally, DWELL detectors use InAs quantum dots embedded in In0.15Ga0.85As wells with GaAs barriers. Intersubband transitions in the conduction band of this system result in infrared detection. InAs quantum dots are grown using self assembly on a GaAs substrate for this system. The strain of the quantum dots and the In0.15Ga0.85As well limits the thickness of the active region. An improved design that minimizes the strain in growth of DWELL active region is discussed. By minimizing the amount of In0.15Ga0.85As in the quantum well, a lower strain per DWELL active region stack is achieved. This design consists of InAs dots in In0.15Ga0.85As/GaAs wells, forming dots-in-a-double-well (DDWELL) is presented. Optimization using PL and AFM is discussed. Detectors fabricated using DDWELL design show an operating temperature of 140 K and a background limited performance at 77 K. A peak detectivity of 6.7x1010 cm.Hz/W was observed for a wavelength of 8.7 μm. In the second part of this dissertation, multispectral and polarization detectors using DWELL absorbers are discussed. Integration of a subwavelength metallic pattern with the detector results in coupling of surface plasmons excited at the metal- semiconductor interface with DWELL active regions. Simulations indicate the presence of several modes of absorption, which can be tuned by changing the pitch of the pattern. Enhancement of absorption is predicted for the detector. Experimental demonstration show spectral tuning in MWIR and LWIR regions and a peak absorption enhancement of 4.9x. By breaking the symmetry of the fabricated pattern, we can extract a polarization dependent response, as shown from device measurements. The technique used is detector agnostic, simple and can easily be transferred to focal plane arrays (FPA). Integrating plasmonic structures on detectors using low noise DDWELL active regions can provide a higher operating temperature and high absorption. The origin of resonant peaks in multispectral DWELL detectors is examined. Use of surface patterns that selectively excite different types of modes, with absorbers of different thicknesses, show the presence of enhancement mechanisms in these devices. A 2.2x enhancement is measured from waveguide modes and 4.9x enhancement is observed from plasmon modes. Finally, a pathway of integration with FPA and integration with other infrared technologies is discussed

3-5족 화합물 반도체의 웨이퍼 접합과 에피택셜 리프트 오프를 통한 다중 파장 광 검출기

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2019. 2. 윤의준.Group III-V compound semiconductors, having a band gap from ultraviolet to infrared regions, have been widely used as imagers to visualize a single band. With the recent arrival of the Internet-of-things (IOTs) era, new applications such as time of flight (TOF) sensors, normalized difference vegetation index (NVDI) and night vision systems have gained interest. Therefore, the importance of multicolor photodetectors is raised. To implement multicolor photodetectors, an epitaxy method has been commonly used with III-V compound semiconductors. For example, quantum wells, quantum dots and type-II based structures and metamorphically grown bulk heteroepitaxial structures have been employed. Although an epitaxy method seems to be quite simple, there are several problems including limitation of material choice due to the discrepancy of lattice constants between thin films and substrates, performance degradation originated from internal defects and complexity of growth. Therefore, to avoid these disadvantages of the epitaxy method, a heterogeneous integration method has been an alternative because the integration of devices grown on different substrates is possible. Thus, it has been considered to be a promising method to combine photodetectors with simple bulk structures. However, although there is a significant advantage to the heterogeneous integration method, current multicolor photodetectors have exhibited limitations regarding pixel density and vertical misalignment due to problems related to conventional integration methods. Therefore, in this thesis, the heterogeneous integration of III-V compound semiconductors was investigated for fabricating multicolor photodetectors with high pixel density and highly accurate alignment. Firstly, a research on heterogeneous integration of GaAs based thin film devices with other substrates was carried out. We studied wafer bonding and epitaxial lift off process which have advantages including large area transferability, cost-effectiveness and high quality of layers compared with wafer splitting and transfer printing methods. To fabricate multicolor photodetectors on single substrates, a stable rigid-to-rigid heterogeneous integration method is highly required. However, there have only been few reports regarding rigid-to-rigid transfer by using epitaxial lift off due to the difficulty involving byproducts and gas bubbles generated during the wet etching of the sacrificial layer for wafer separation. This has been a hindrance compared with thin film on flexible substrates which can accelerate wafer separation by using strain and external equipment. In order to overcome this problem, high throughput epitaxial lift off process was proposed through a pre-patterning process and surface hydrophilization. The pre-patterning process can maximize the etching area of the AlAs sacrificial layer and rapidly remove bubbles. In addition, acetone, which is a hydrophilic solution, was mixed with hydrofluoric acid in order to reduce the surface contact angle and viscosity. It resulted in an effective penetration of the etching solution and the suppression of byproducts. Consequently, it was possible to transfer GaAs thin films on rigid substrates within 30 minutes for a 2 inch wafer which has been the fastest compared with previous reports. Also, using this template, electronic and optoelectronic devices were successfully fabricated and operated. Secondly, we have studied to overcome restrictions of bulk photodetector for InSb binary material including the detection limit and cryogenic operation. To extend the detection limit of bulk InSb toward the LWIR range, the ideal candidate of III-V bulk materials is indium arsenide antimonide (InAsSb) material due to its corresponding band gaps ranging from SWIR to LWIR. By combining bulk InAsSb with other bulk materials with previously developed integration methods, we could ultimately fabricate a multicolor photodetector ranging from ultraviolet to LWIR with only bulk structures. Thus, in order to verify the viability of this material, a p-i-n structure based photodetector with an InAs0.81Sb0.19 absorption layer was grown on a GaAs substrate. To enhance an ability to be operated at a high temperature, an optimum InAlSb barrier layer was designed by technology computer aided design (TCAD). Also, InAsSb/InAlSb heterojunction photodetector was grown by molecular beam epitaxy (MBE). As a result, we have demonstrated the first room temperature operation of heterojunction photodetectors in MWIR range among InAsSb photodetectors with similar Sb compositions. Additionally, it has a higher responsivity of 15 mA/W compared with commercialized photodetectors. This MWIR photodetector with room temperature operability could help the reduction of the volume for final detector systems due to the elimination of Dewar used in InSb photodetectors. In other words, from this experiments, it is suggested that there is a strong potential of InAsSb bulk structures for detecting LWIR. Finally, the study on the monolithic integration was carried out to verify the feasibility of multicolor photodetectors by integration of bulk structures. Among procured photodetectors with detection ranging from visible to MWIR at room temperature operation, visible GaAs and near-infrared InGaAs photodetector were used for establishing the optimized fabrication process due to materials process maturity. By using previously developed high throughput ELO process, GaAs photodetectors were transferred onto InGaAs photodetectors to form visible/near-infrared multicolor photodetectors. It was found that top GaAs PD and bottom InGaAs PD were vertically well aligned without an off-axis tilt in x-ray diffraction (XRD) measurement. Also, similar dark currents of each photodetector were observed compared with reference photodetectors. Finally, with incidence of laser illumination, photoresponses were clearly revealed in visible band and near-infrared band of material characteristics, respectively. These results suggested high throughput ELO process enables the monolithic integration of bulk based multicolor photodetectors on a single substrate with high pixel density and nearly perfect vertical alignment. In the future, depending on the target applications, photodetectors with desired wavelengths could be simply grown as bulk structures and fabricated for multicolor imagers.자외선부터 적외선 영역의 밴드갭을 가진 3-5족 화합물 반도체는 단일 파장대역을 시각화하는 imager 로 널리 사용되고 있다. 그러나, 최근 사물인터넷 시대가 도래함에 따라, time of flight (TOF) 센서, 식생지수 측정, night vision 등의 새로운 응용처가 증가하고 있다. 따라서 기존의 단일파장 광 검출기가 아닌, 다중파장 광 검출기의 중요성이 증대되고 있으며, 이런 다중파장 광 검출기를 구현하기 위해서 3-5족을 화합물 반도체의 epitaxy 방법이 흔히 사용되어 왔다. 예를 들어, 다른 격자 상수를 가진 벌크 구조를 metamorphic 성장법을 이용하여 성장하거나, 또는 양자우물, 양자점 그리고 type-II 기반의 구조가 적용되어야만 했다. Epitaxy 방법은 매우 간단한 방법처럼 보이지만, 기판과 성장하려는 물질간의 격자상수의 차이로 인해 제한되는 물질 선택, 내부 결함에 의한 성능감소 그리고 성장의 복잡함 등 여러 문제가 존재한다. 그래서, epitaxy 방법의 단점들을 회피하기 위하여, 다른 기판에서 성장된 소자의 집적을 가능하게 할 수 있는, 이종 집적 방법이 대안이 되어왔다. 이를 이용하면, 간단한 벌크 구조의 광 검출기를 결합할 수 있기 때문에 매우 유망한 방법으로 여겨지고 있다. 그러나, 이종 집적 방법의 뛰어난 장점에도 불구하고, 현재의 다중파장 광 검출기는 집적 방법의 문제로 수직 정렬 오차 및 픽셀 밀도 측면에서 한계점을 보여주었다. 따라서, 본 논문에서는 고밀도/ 고정렬된 다중파장 광 검출기 제작을 위한 3-5족 기반의 화합물 반도체의 이종 집적 방법에 대한 연구를 진행하였다. 먼저, 3-5족 GaAs 기반의 박막소자를 다른 기판과 이종 집적하는 연구를 수행하였다. 기존의 wafer splitting 과 transfer printing 방법과 비교했을 때 대면적 전사, 저렴한 가격 그리고 고품질 layer등 장점들이 있는 웨이퍼 접합과 에피택셜 리프트 오프 (epitaxial lift off) 방법에 대해서 연구를 하였다. 단일 기판상에 다중파장 광 검출기를 제작하기 위해서는, rigid-to-rigid 이종 집적 방법이 반드시 필요하다. 그러나, strain 과 외부 장치를 이용하여 기판 분리를 가속화 시킬 수 있는 유연기판 상의 박막전사와 달리, 습식 식각 시 생성되는 부산물들과 가스 기포들 때문에 에피택셜 리프트 오프 방법을 이용한 rigid-to-rigid 전사에 대해서는 매우 적은 결과만이 보고되었다. 이런 문제를 극복하기 위해서, pre-patterning 과정과 표면 친수화를 통한 고속 에피택셜 리프트 오프를 제안하였다. 이 pre-patterning 과정은 AlAs 희생층의 식각 영역을 극대화 시킬 수 있으며, 기포를 빠르게 제거할 수 있다. 그리고, 친수성 용액인 아세톤을 불산과 섞어주면 점도와 표면 접촉 각을 줄일 수 있다. 이것은 식각 용액의 효과적인 침투와 부산물을 억제시키는 결과를 보였다. 결과적으로, 2 인치 크기의GaAs 기반 박막들을 rigid 기판상에 30분 이내로 전사가 가능했으며 이는 기존의 보고들과 비교했을 때 가장 빠른 결과이다. 또한 이 템플릿을 이용하여 광/전자 소자를 성공적으로 제작 및 동작시켰다. 두 번째로, 기존의 InSb 물질을 이용한 벌크 구조의 광 검출기가 가진 파장한계 그리고 저온동작 등의 제약들을 극복하기 위한 연구를 진행하였다. 벌크 구조의 파장 한계를 원적외선 대역까지 늘이기 위한, 3-5족 물질 중 이상적인 물질은 인듐 아세나이드 안티모나이드 (indium arsenide antimonide) 이다. 왜냐하면 InAsxSb1-x는 SWIR 부터 LWIR 의 해당하는 밴드 갭을 가지고 있기 때문이다. 이 물질 기반의 구조와 개발된 공정을 사용하면, 우리는 궁극적으로 자외선부터 원적외선까지의 영역을 벌크 구조만을 사용하여 다중파장 광 검출기를 구현할 수 있게 된다. 따라서, 이 물질의 가능성을 검증하기 위해서, InAs0.81Sb0.19 의 흡수층을 가진 p-i-n 구조 기반의 광 검출기를 GaAs 기판상에서 성장하였다. 고온에서 동작 특성을 향상시키기 위하여, 최적의 InAlSb 배리어를 TCAD로 디자인하였다. 이러한, InAsSb/InAlSb 이종 접합 광 검출기는 분자선 증착 장비를 이용하여 성장되었다. 그 결과로, 우리는 비슷한 Sb 조성을 가진 InAsSb 기반의 광 검출기들 중에서, 처음으로 중적외선 대역의 이종 접합 구조의 광 검출기를 상온 동작 하는 것을 시연하였다. 게다가, 그것은 상용화 된 광 검출기보다 높은 광 응답 특성(15 mA/W)을 보여주었다. 이 상온에서 동작하는 중적외선 광 검출기는 InSb 광 검출기에 사용되는 Dewar 를 제거함으로써, 최종 검출기 시스템의 부피를 감소 시킬 수 있다. 이 실험으로부터, 벌크 구조로 원적외선 대역을 검출하기 위한 InAsSb 물질의 큰 잠재성이 있다는 것을 의미한다. 마지막으로, 벌크 구조의 집적을 통한 다중파장 광 검출기의 실현이 가능한지 확인하기 위해서 모놀리식(monolithic) 집적에 관한 연구를 수행하였다. 확보된 상온 동작이 가능한 가시광선부터 MWIR 검출 파장을 가진 광 검출기들 중에서, 최적의 제작 순서를 확립하기 위해서 물질에 관한 성숙도가 높은 가시광선 GaAs 그리고 근적외선 InGaAs 광 검출기를 사용하였다. 가시광/근적외선 대역의 다중파장 광 검출기를 형성하기 위해서, GaAs 광 검출기를 InGaAs 광 검출기 상으로 개발된 고속 에피택셜 리프트 오프 기법을 사용하여 전사하였다. GaAs 광 검출기와 InGaAs 광 검출기는 off-axis 없이 수직으로 잘 정렬되었음을 x-ray 분광법을 이용하여 확인하였다. 또한, 각각의 광 검출기의 기준 소자들과 비교했을 때 비슷한 암 전류가 나타났다. 마지막으로, 레이저 입사를 통해, 두 개의 광 검출기 대한 광 반응은 물질 특성들에 따라 가시광과 근적외선에서 각각 명확하게 나타났다. 이러한 결과들은 고속 에피택셜 리프트 오프 기법이 높은 픽셀 밀도 및 거의 완벽한 수직 정렬도를 갖는 한 기판상의 벌크 기반의 다중파장 광 검출기를 집적할 수 있다는 것을 의미한다. 미래의 목표하는 응용처에 따라, 원하는 파장들을 갖는 광 검출기를 벌크 구조로 간단하게 성장할 수 있고, 다중파장 이미징 시스템을 제작 할 수 있다.List of Figures i Chapter.1 Introduction 1 1.1 Photodetectors based on III-V compound semiconductors 1 1.2 Imaging applications 4 1.2.1. Single color imaing 4 1.2.2. Multicolor imaing 4 1.2.3. Development trend of photodetectors 5 1.3 Approches for forming multicolor photodectors 9 1.3.1. Epitaxy 9 1.3.2. Heterogeneous integration 17 1.3.3. Summary of each method 21 1.4 Overview of heterogeneous integration technology 23 1.4.1. Introduction 23 1.4.2. Direct bonding 24 1.4.3. Cold-weld bonding 26 1.4.4. Eutectic bonding 26 1.4.5. Adhesive bonding 28 1.4.7. Wafer splitting 31 1.4.8. Epitaxial lift off (ELO) 33 1.4.9. Benchmark of differenct heterogeneous intergration methods 35 1.5 Thesis overview 37 1.6 Bibliography 40 Chapter. 2 Method for heterogeneous integration of III-V compound semiconductors on other substrates 45 2.1 Introduction 45 2.1.1 The origin of low throughput in conventional ELO 46 2.1.2 Previous works for ehancement of ELO throughput 48 2.1.3 Approach: high-throughput ELO process 53 2.1.4 Experimental procedure 55 2.2 Results and discussion 57 2.3 Summary 65 2.4 Biblography 66 Chapter. 3 Verification of thin film devices by using a high throughput heterogeneous integration method 70 3.1 Introduction 70 3.2 Growth of device structures and heterogeneous integration 72 3.2.1. Device structures 72 3.2.2. Wafer bonding and ELO 74 3.3 Y2O3 bonded HEMTs on Si substrate 75 3.3.1 Fabrication process 75 3.3.2. Material characterization of HEMTs on Si 76 3.3.3. Electrical characterization of HEMTs on Si 80 3.3.4. Investigation of wafer reusability by using HEMT structure 83 3.4 Pt/Au bonded optoelectonic devices 86 3.4.1. Fabrication process of solar cells and HPTs on Si 86 3.4.2. Evaluation of Pt/Au metal bonding 88 3.4.3. Characterization of solar cells and HPTs 91 3.5 Estimation of production cost via recycling III-V wafers 95 3.6 Summary 101 3.7 Bibliography 102 Chapter. 4 Design and characterization of III-V based photodtectors 106 4.1 Introduction 106 4.1.1. The potential of Induim arsenide antimonide (InAsSb) 106 4.1.2. Challenges of InAsSb p-i-n PDs for compact detector systems 110 4.2 Barrier layer design and material characterization for growing HJPDs 113 4.2.1. Simulation of an optimum barrier layer for InAs0.8Sb0.2 113 4.2.2. Growth of a high quality InAsSb layer with an AlGaSb buffer layer grown on GaAs substrates 115 4.2.3. Ohmic contact formation with metal species 120 4.2.4. Growth and fabrication of InAsSb based HJPDs 126 4.3 Analysis of electrical and optical characteristics for fabricated PDs 129 4.4 Summary 138 4.5 Bibliography 139 Chapter. 5 Monolithic integration of visible/near-infrared photodetectors 145 5.1 Introduction 145 5.2 Fabrication process and material characterization of multicolor PD 148 5.3 Analysis of the electrical and optical characteristics of the fabricated multicolor PDs 154 5.4 Summary 163 5.5 Bibliography 164 Chapter. 6 Conclusions 169 국 문 초 록 172Docto

Center for Space Microelectronics Technology. 1993 Technical Report

The 1993 Technical Report of the Jet Propulsion Laboratory Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the Center during the past year. The report lists 170 publications, 193 presentations, and 84 New Technology Reports and patents. The 1993 Technical Report of the Jet Propulsion Laboratory Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the Center during the past year. The report lists 170 publications, 193 presentations, and 84 New Technology Reports and patents

Mid-IR type-II InAs/GaSb nanoscale superlattice sensors

The detection of mid-wavelength infrared radiation (MWIR) is very important for many military, industrial and biomedical applications. Present-day commercially available uncooled IR sensors operating in MWIR region (2-5μm) use microbolometric detectors which are inherently slow. Available photon detectors (mercury cadmium telluride (MCT), bulk InSb and quantum well infrared detectors (QWIPs))overcome this limitation. However, there are some fundamental issues decreasing their performance and ability for high temperature operation, including fast Auger recombination rates and high thermal generation rate. These detectors operate at low temperatures (77K-200K) in order to obtain high signal to noise ratio. The requirement of cooling limits the lifetime, increases the weight and the total cost, as well as the power budget, of the whole infrared system. In recent years, InAs/GaSb superlattice based detectors have appeared as an interesting alternative to the present-day IR detector systems. These heterostructures have a type-II band alignment such that the conduction band of InAs layer is lower than the valence band of GaSb layer. The effective bandgap of these structures can be adjusted from 0.4 eV to values below 0.1 eV by varying the thickness of constituent layers leading to an enormous range of detector cutoff wavelengths (3-30μm). The InAs/GaSb SLs have a higher degree of uniformity than the MCT alloys, making them attractive for large area focal plane arrays. They provide a smaller leakage current due to larger effective electron mass, which suppresses tunneling. This material system is also characterized by high operating temperatures and long Auger recombination rates. This suggests the potential for using the SLs technology for realizing high operating temperature devices. This work is focused on the development of mid-IR InAs/GaSb SLs sensors with high-operating temperature. Contributions of this thesis include 1) development of growth and processing procedure for the n-on-p and p-on-n design of SL detectors leading to improved detector performance, 2) careful evaluation of characteristics of SL detectors, 3) methods of reduction of surface component of dark current passivation techniques)

Hybrid Organic/Inorganic Optical Upconversion Devices

The widely available charge coupled device (CCD) and lately CMOS imaging devices have created many applications on a mass scale. However these devices are limited to wavelengths shorter than about 1 μm. Hybrid photon upconversion devices have been developed recently. The end goal is to achieve an alternative technology for imaging in the 1.5-μm region. The hybrid upconversion idea relies on the integration of a photodetector and an organic light emitting diode (OLED). Under a forward bias for the OLED, the detected signal in the Photodetector is sent to the OLED, resulting in an increase in emission at a shorter wavelength and therefore achieving optical up conversion. An OLED device can simply consists of a stack of anode, a hole transport layer (HTL), a light-emitting layer, an electron transport layer (ETL), a cathode layer, and it typically emits visible light. As each organic molecule is a topologically perfect structure, the growth of each organic layer does not require “lattice matching”, which has been the fundamental limit for inorganic semiconductor monolithic devices. Thus, integration of an OLED with a III–V compound semiconductor is a highly feasible and desirable approach for making low-cost, large-area, potentially high efficiency devices. This thesis addresses the physics, fabrication and characterization of hybrid near infrared optical upconverters and their imaging application. Firstly, one novel hybrid optical upconverter structure is presented, which substantially improves the upconversion efficiency by embedding a metal mirror. Efficient carrier injection from the inorganic photodetector to the OLED is achieved by the insertion of a thin Au metal embedded mirror at the inorganic-organic interface. The upconversion efficiency was improved by more than 100%. Secondly, the overall upconversion efficiency can be increased significantly, by introducing a gain mechanism into the Photodetector section of the upconverter. A promising option to implement gain is a heterojunction phototransistor (HPT). An InGaAs-InP HPT was integrated with an OLED, which converts 1.5-μm Infrared light to visible light with a built-in electrical gain (~94). The overall upconversion efficiency was improved to be 1.55 W/W. Thirdly, this upconversion approach can also be used to realize a pixelless imaging device. A pixelless hybrid upconversion device consists of a large-area single-mesa device, where the OLED output is spatially correlated with the input 1.5-µm scene. Only the parts receiving incoming photons will emit output photons. To achieve this functionality, photon-generated carriers must flow mainly along the layer-growth direction when injected from the InGaAs light absorption layer into OLED light emission layer. A prototype of pixelless imaging device based on an i-In0.53Ga0.47As/C60 heterojunction was demonstrated, which minimized lateral current spreading. This thesis presents experimental results of the first organic/inorganic hybrid optical amplifer and the first hybrid near infrared imaging device

Quantum well intersubband photodetectors in focal plane arrays

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1996.Includes bibliographical references (p. 235-246).by Paul Scott Martin.Ph.D