ELEMENTAL BORON-DOPED P+-SIGE LAYERS GROWN BY MOLECULAR-BEAM EPITAXY FOR INFRARED DETECTOR APPLICATIONS

SiGe/Si heterojunction internal photoemission (HIP) detectors have been fabricated utilizing molecular beam epitaxy of p+-SiGe layers on p--Si substrates. Elemental boron from a high-temperature effusion cell was used as the dopant source during molecular beam epitaxy (MBE) growth, and high doping concentrations (> 5 x 10(20) cm-3) have been achieved. Strong infrared absorption, mainly by free-carrier absorption, was observed for the degenerately doped SiGe layers. The use of elemental boron as the dopant source allows a low MBE growth temperature (350-degree-C), resulting in improved crystalline quality and smooth surface morphology of the Si0.7Ge0.3 layers. Nearly ideal thermionic emission dark current characteristics have been obtained. Photoresponse of the HIP detectors in the long-wavelength infrared regime has been demonstrated.