Experimental and theoretical investigation of detection wavelength tuning in quantum well infrared-photodetectors by quantum well intermixing technique

Detection wavelength tuning of quantum well infrared photodetector (QWIP) has been carried out by using impurity free vacancy disordering (IFVD) technique with SiO₂ capping layer. The detection wavelength of QWIP was changed from 8.2μm to 10μm due to bandgap change by intermixing of constituent atoms in multiple quantum well (MQW) absorption region in Fig.1. The red-shift in detection wavelength can be explained by gap narrowing between confined state and continuum state in conduction band, which is a consequence of blue-shift in MQW bandgap after intermixing in Fig.2. The bandgap of the intermixed MQW structure was theoretically investigated. The Al-Ga inter-diffusion, which induces the red-shift of detection wavelength from 8.2μm to 10μm, was calculated to be 7Å at 850°C.