Highly strained [formula omitted] layers for short wavelength QWIP and QCL structures grown by MBE

Abstract

Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on In x Ga (1−x) As−In y Al (1−y) As (x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of ∼420°C to produce structures that are suitable for both emission and detection in the 2– 5 μm mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In 0.84Ga 0.16As/AlAs/In 0.52Al 0.48As double barrier quantum wells grown on InP substrates is demonstrated. Γ– Γ intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2– 7 μm ) in three structures of differing In 0.84Ga 0.16As well width (30, 45, and 80 A ̊ ). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs–InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the Γ– Γ bands and the Γ–X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated.