Raster-scan imaging with normal-incidence, midinfrared InAs/GaAs quantum dot infrared photodetectors

We demonstrate normal incidence infrared imaging with quantum dot infrared photodetectors using a raster-scan technique. The device heterostructure, containing multiple layers of InAs/GaAs self-organized quantum dots, were grown by molecular-beam epitaxy. Individual devices have been operated at temperatures as high as 150 K and, at 100 K, are characterized by λpeak = 3.72 μm,λpeak=3.72μm, Jdark = 6×10−10 A/cm2Jdark=6×10−10A/cm2 for a bias of 0.1 V, and D∗ = 2.94×109 cm Hz1/2/WD∗=2.94×109cmHz1/2/W at a bias of 0.2 V. Raster-scan images of heated objects and infrared light sources were obtained with a small (13×13)(13×13) interconnected array of detectors (to increase the photocurrent) at 80 K. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70691/2/APPLAB-80-18-3265-1.pd

High-performance mid-infrared quantum dot infrared photodetectors

Quantum dot infrared photodetectors (QDIPs) have emerged as attractive devices for sensing long wavelength radiation. Their principle of operation is based on intersublevel transitions in quantum dots (QDs). Three-dimensional quantum confinement offers the advantages of normal incidence operation, low dark currents and high-temperature operation. The performance characteristics of mid-infrared devices with three kinds of novel heterostructures in the active region are described here. These are a device with upto 70 QD layers, a device with a superlattice in the active region, and a tunnel QDIP. Low dark currents (1.59 A cm−2 at 300 K), large responsivity (2.5 A W−1 at 78 K) and large specific detectivity (1011 cm Hz1/2 W−1 at 100 K) are measured in these devices. It is evident that QDIPs will find application in the design of high-temperature focal plane arrays. Imaging with small QD detector arrays using the raster scanning technique is also demonstrated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48926/2/d5_13_009.pd

Intersubband absorption in annealed InAs/GaAs quantum dots: a case for polarization-sensitive infrared detection

We have studied the characteristics of intersubband absorption of polarized infrared (IR) radiation in as-grown and annealed self-organized InAs/GaAs quantum dots. It is observed that with the increase of annealing time and temperature, the dots tend to flatten and behave more like quantum wells. As a result, their sensitivity to TE (in-plane)-polarized light decreases and that to TM (out-of-plane)-polarized light increases. The effect could be utilized for the realization of polarization-sensitive IR detectors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48917/2/d31508.pd

UV- and RIR-MAPLE: Fundamentals and applications

Laser beams are powerful tools for diagnostic purposes and growth of thin films. However, the interaction of lasers with organic or biological materials may result in laser-induced photo-chemical and photo-thermal damage to the materials of interest. In order to reduce these effects, the matrix-assisted pulsed laser evaporation (MAPLE) technique was introduced for thin film deposition with the possibility to use two different wavelength ranges to induce target ablation: laser absorption by the matrix (UV-MAPLE) or direct laser excitation of vibrational frequency of the matrix constituent bonds (RIR-MAPLE). In this chapter, the UV-MAPLE physical working principles will be outlined together with its applications and latest results. The RIR-MAPLE working principle and applications to materials of interest for optoelectronics applications will be described and discussed also, with particular attention to the emulsion-based RIR-MAPLE approach relating the film properties with the physical-chemical properties of the emulsion components (primary and secondary solvent, surfactant and matrix)

Influence of rapid thermal annealing on a 30 stack InAs/GaAs quantum dot infrared photodetector

In this article the effect of rapid thermal annealing (RTA) on a 30 stacked InAs/GaAs, molecular beam epitaxially grown quantum dot infrared photodetector (QDIP) device is studied. Temperatures in the range of 600–800 °C for 60 s, typical of atomic interdiffusion methods are used. After rapid thermal annealing the devices exhibited large dark currents and no photoresponse could be measured. Double crystal x-ray diffraction and cross sectional transmission electron microscopy studies indicate that this could be the result of strain relaxation. V-shaped dislocations which extended across many quantum dot (QD) layers formed in the RTA samples. Smaller defect centers were observed throughout the as-grown sample and are also likely a strain relaxation mechanism. This supports the idea that strained structures containing dislocations are more likely to relax via the formation of dislocations and/or the propagation of existing dislocations, instead of creating atomic interdiffusion during RTA. Photoluminescence (PL) studies also found that Si related complexes developed in the Si doped GaAs contact layers with RTA. The PL from these Si related complexes overlaps and dominates the PL from our QD ground state. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69370/2/JAPIAU-94-8-5283-1.pd

Doping characterization of InAs/GaAs quantum dot heterostructure by cross-sectional scanning capacitance microscopy

In order to better understand dopant incorporation in quantum dot infrared photodetectors, the application of cross-sectional scanning capacitance microscopy (SCM) has been used to investigate carrier occupation/distribution in a multilayer InAs/GaAs quantum dot (QD) heterostructure for different doping techniques. The doping schemes in the QD structure include direct doping (in InAs QD layers) and remote doping (in GaAs barrier layers), each with different doping concentrations. The SCM image suggests that large band bending occurs due to highly doped, remote-doping layers, thereby causing electron redistribution in direct-doping layers. The experimental result is supported by a band structure calculation using the Schrödinger–Poisson method by NEXTNANO3.Author has checked copyright12/12/2013. SB