Highly strained InxGa(1−x)As−InyAl(1−y)As (x>0.8,y<0.3) layers for short wavelength QWIP and QCL structures grown by MBE

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 . 8 4 Ga 0 . 1 6 As/AlAs/In 0 . 5 2 Al 0 . 4 8 As 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 . 8 4 Ga 0 . 1 6 As 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 F-F 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.