The model and stress analysis of self-doping SiGe/Si multi-quantum wells applied in uncooled infrared focal plane array

Abstract

Silicon-germanium multi-quantum wells (MQWs) film is a promising sensitive material with high temperature coefficient of resistance (TCR). This paper focuses on solving the stress problem of uncooled infrared focal plane array caused by intrinsic stress of MQWs films. First of all, the paper presents the accurate TCR model of MQWs, which is more consistent with the actual situation especially when the Fermi level enters the valence band. The energy bands distributions and each sub-band wavefunction of MQWs were calculated. The critical thickness analysis about epitaxial growth film was carried out for solving intrinsic stress of MQWs film, which leads to the deformation of pixel structure in the fabrication processes. The paper calculated the maximum film stress in completely strain state and derived the buckling of the bolometer. Tri-layer structure was applied in support beam design for the deformation compensation. The self-doping MQWs film was epitaxial growth on silicon substrate with buffer layer to overcome the lattice slips in experiments. The bolometer was fabricated and released without visible deformation utilizing the compensation methods. The ohmic-contact problems and signals were also mentioned in the paper. The thermal conductivity and capacity were calculated by means of thermal response experiments without infrared radiation.