Advanced semiconductor quantum well devices for infrared applications

High performance mid-wavelength infrared (MWIR) light emitting diodes (LEDs) are needed for chemical sensing, analysis and medical imaging. Efficient long wavelength infrared (LWIR) photodetectors are highly desirable for remote sensing and space exploration. The goal of this work is to investigate new mid-infrared LEDs and to optimize existing LWIR quantum well infrared photodetectors (QWIPs).; Type-II "W" InAs/InGaSb/AlGaAsSb quantum wells were incorporated as optically active layers in MWIR LEDs. Influence of MBE crystal growth conditions on the density of Shockley-Read-Hall centers in the "W" quantum wells was studied and the optimal growth conditions were identified. A qualitative physical model was developed to describe relative importance of the radiative and non-radiative processes for various temperature ranges. MWIR LED structures lattice-matched to InAs and GaSb substrates were grown. Devices on InAs substrates were found to be at least twice as efficient as devices grown on GaSb. LEDs on InAs had 4.5 mum emission wavelength and 26.5 muW/A external efficiency.; Possibility to operate GaAs/AIGaAs QWIP under normal-to-surface light incidence was studied. Metal nano-particle surface coating was developed and processes responsible for, light coupling into the QWIP were investigated. QWIP structure itself was optimized to eliminate Si-diffusion-assisted dark current enhancement by employing a new doping profile in the quantum wells. Devices with the new doping profile had an order of magnitude lower dark current and 20% higher photoresponse than commercially available QWIPs.