Thin-film quantum dot photodiode for monolithic infrared image sensors

Imaging in the infrared wavelength range has been fundamental in scientific, military and surveillance applications. Currently, it is a crucial enabler of new industries such as autonomous mobility (for obstacle detection), augmented reality (for eye tracking) and biometrics. Ubiquitous deployment of infrared cameras (on a scale similar to visible cameras) is however prevented by high manufacturing cost and low resolution related to the need of using image sensors based on flip-chip hybridization. One way to enable monolithic integration is by replacing expensive, small-scale III-V-based detector chips with narrow bandgap thin-films compatible with 8- and 12-inch full-wafer processing. This work describes a CMOS-compatible pixel stack based on lead sulfide quantum dots (PbS QD) with tunable absorption peak. Photodiode with a 150-nm thick absorber in an inverted architecture shows dark current of 10(-6) A/cm(2) at 2 V reverse bias and EQE above 20% at 1440 nm wavelength. Optical modeling for top illumination architecture can improve the contact transparency to 70%. Additional cooling (193 K) can improve the sensitivity to 60 dB. This stack can be integrated on a CMOS ROIC, enabling order-of-magnitude cost reduction for infrared sensors

Ligand Exchange Optimization for Quantum Dot Based Infrared Thin-film Photodetectors

Image in the infrared wavelength range offers several advantages when compared with the visible range. The information that is impossible to acquire with our naked eyes can be used for different industries such as quality control, surveillance, augmented and virtual reality, medical diagnostics, and others. Colloidal quantum dots (QDs) have been gathering increased attention and becoming one of the most promising candidates for infrared optoelectronic devices, being praised for their size-dependent bandgap tunability, low-cost manufacturing when comparing to III-V semiconductors, and suitability for deposition on large and flexible substrates. However, the main challenge to accomplish is precise control over their material properties through surface passivation. The work performed in this thesis is focused on exploring the effect of different strategies of surface ligand treatments to colloidal QDs for further integration as an active layer of thin-film photodetectors. Therefore, thin-films made from solution-phase ligand exchange lead sulfide (PbS) QDs deposited on glass substrates were analyzed in terms of their optical and morphological properties through multiple characterization techniques. Full processing and fabrication of thin-film photodiode detectors were then carried out, pursuing the highest devices performance according to their electrical characterization. In the end, the developed PbS QD-based photodiode stack successfully completed the proposed optimization by reaching dark currents values close to 10-5 A/cm2 at -3 V and external quantum efficiency of 29% at 1450 nm

Miniaturized Silicon Photodetectors

Silicon (Si) technologies provide an excellent platform for the design of microsystems where photonic and microelectronic functionalities are monolithically integrated on the same substrate. In recent years, a variety of passive and active Si photonic devices have been developed, and among them, photodetectors have attracted particular interest from the scientific community. Si photodiodes are typically designed to operate at visible wavelengths, but, unfortunately, their employment in the infrared (IR) range is limited due to the neglectable Si absorption over 1100 nm, even though the use of germanium (Ge) grown on Si has historically allowed operations to be extended up to 1550 nm. In recent years, significant progress has been achieved both by improving the performance of Si-based photodetectors in the visible range and by extending their operation to infrared wavelengths. Near-infrared (NIR) SiGe photodetectors have been demonstrated to have a “zero change” CMOS process flow, while the investigation of new effects and structures has shown that an all-Si approach could be a viable option to construct devices comparable with Ge technology. In addition, the capability to integrate new emerging 2D and 3D materials with Si, together with the capability of manufacturing devices at the nanometric scale, has led to the development of new device families with unexpected performance. Accordingly, this Special Issue of Micromachines seeks to showcase research papers, short communications, and review articles that show the most recent advances in the field of silicon photodetectors and their respective applications

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

PbS colloidal quantum dots based photodetectors for integrated SWIR detection

Due to the low water absorption and nightglow, sensing in short wave infrared (SWIR) is very attractive in applications such as; passive night vision, biomedical imaging and remote sensing. The monolithic integration of photodetectors to the readout circuits is desirable in many applications to increase density of detectors and reduce costs, system size and power consumption. Solution-processed semiconductors are a promising alternative to conventional bulk crystalline photodetectors since their production is low cost and easy, their bandgap can be tuned depending on their sizes, and they can be easily integrated on any substrate. In this work, PbS colloidal quantum dot based photodiodes are realized that are compatible with the integration on Read Out Integrated Circuits (ROIC). Various kinds of PbS quantum dots based schottky diodes are designed on glass and silicon substrates. Spin deposition steps and solid state ligand exchange processes are optimized to create pinhole free and high mobility PbS quantum dot layers. In addition to that Integrated Circuit (IC) compatible versions of PbS colloidal quantum dot (CQD) photodiodes are realized. ROIC chip surface is mimicked on Si substrates and fabrication steps are optimized for integration. Special importance is given to optimize highly conductive and transparent indium tin oxide layer using DC magnetron sputtering. Sensitivities of 1.4x1012 Jones, comparable to the conventionally used crystalline, bulk photodetectors is achieved. Also, plasmonic scattering effects of metal nanoparticles in PbS CQD layer are studied. Absorption and responsivity enhancement of 6 fold is presented using gold nanoparticles in PbS CQD based photoconductors

III-V Quantum Structured Infrared Photodetectors Directly Grown on Silicon

Direct growth of III-V infrared photodetectors on silicon substrates is a promising so- lution for realising low-cost and large-format infrared focal plane arrays. However, this heteroepitaxial growth technique will generate various defects due to the dissimilarities between III-V materials and Si. These defects can severely damage the performance of a detector. In this thesis, different III-V quantum structured infrared photodetectors directly grown on Si are investigated to understand how different structures react to the defects. The experimental chapters begin with reporting an InGaAs/GaAs quantum dot infrared pho- todetector (QDIP) on Si. By utilising a Si substrate with a high degree of offcut along with dislocation filter layers, antiphase domains have been eliminated and the threading dislocation density has been reduced by ∼4 orders of magnitude. The QDIP shows a dual-band photoresponse at 80 K. To reduce the noise, a sub-monolayer QD quantum cascade photodetector on Si was designed. This structure has led to a distinct reduction of dark current and noise, achieving a high operating temperature of 160 K. To further boost the quantum efficiency of infrared photodetectors on Si, InAs/GaSb type-II superlattice (T2SL) photodetectors were also studied in this thesis. Generally, T2SL photodiode structures are more sensitive to material defects than QDs. Moreover, the surface leakage current contributes to a high level of dark current. InAs/GaSb T2SL photodiodes and barrier detectors have been grown on GaAs and Si substrates. Transmission electron microscopy and X-ray diffraction results confirm that the strain energy has been released at the heteroepitaxy interface and the threading dislocation density has been reduced by ∼3 orders of magnitude. The bulk dark current has been reduced by implementing an nBp barrier design. As a result, a T2SL nBp detector on GaAs with surface passivation has been shown to be capable of operating at 190 K without external bias. The work described in this thesis shows that there is great potential to improve the detector performance by using novel detector designs. Future work should focus on structure optimisation, as well as material quality im- provements, in order to achieve both low dark current and high quantum efficiency. High- operating temperature detectors on Si can be attempted to further explore the potential of III-V quantum structured infrared photodetectors. Specific recommendations are made for candidate structures. In order to be compatible with the mainstream Si micro-electronics industry, fabrication on (001) Si substrates will be required. Research towards this objec- tive is therefore also proposed

Development of type II superlattice infrared detectors monolithically integrated on silicon substrates

The project’s objective is the development of an InAs/GaSb type II superlattice (T2SL) medium wavelength infrared photodiode directly grown on Si substrate for the use of an infrared single pixel photodiode. The T2SL has been selected as the replacement for the state-of-the-art CdHgTe (CMT). The use of Si substrate will help with the integration into the Si-based technology by reducing the fabrication process and costs. The T2SL is a photon detector with overlapping multiple quantum well structure and a type 2 bandgap alignment. The T2SL are fabricated using a combination of materials from the group III-V in order to achieve a well-controlled ultra-thin heterostructures using molecular beam epitaxy as a growth technique. The structure within the active region is designed to enhance the performance of the T2SL architecture by manipulating the thickness and doping of each layer. The direct growth of a T2SL structure on the Si substrate has achieved similar structural and optical properties when compared to that grown on the GaAs substrate. The Si architecture has an absorption edge of 5.365μm when measured at 70K: dark current density at -1V is 4x101A/cm2; responsivity (R) peak is 1.2A/W; quantum efficiency (QE) at -0.1V is 32.5%; and specific detectivity (D*) peak is 1x109cmHz½/W. The pπBn has best architecture over GaAs substrate due to the wide bandgap unipolar barrier. The pπBn has an absorption edge of 6.5 μm when measured at 77K: dark current density under -0.6V is 5x10-3A/cm2; R peak is 0.6A/W; QE at 0V and 3.25μm is 23%; and D* peak is 1x1011cmHz½/W. These results demonstrate that the D* of the pπBn structure is just one order of magnitude smaller than the state-of-the-art CMT detector which is 2x1012cmHz1/2W

Road Map for Nanocrystal Based Infrared Photodetectors

Infrared (IR) sensors based on epitaxially grown semiconductors face two main challenges which are their prohibitive cost and the difficulty to rise the operating temperature. The quest for alternative technologies which will tackle these two difficulties requires the development of new IR active materials. Over the past decade, significant progresses have been achieved. In this perspective, we summarize the current state of the art relative to nanocrystal based IR sensing and stress the main materials, devices and industrial challenges which will have to be addressed over the 5 next years