NOVEL SI1-XGEX/SI HETEROJUNCTION INTERNAL PHOTOEMISSION LONG-WAVELENGTH INFRARED DETECTORS

A new approach to the design of a Si-based infrared detector is demonstrated, based on internal photoemission over a Si1-xGe x/Si heterojunction barrier. The heterojunction internal photoemission device structure is grown by molecular beam epitaxy (MBE). The detector requires a degenerately doped p+-Si1-xGe x layer for strong infrared absorption and photoresponse. Doping concentrations to 1020 cm-3 are achieved using boron from a HBO2 source during MBE growth of the Si1-xGex layers. The photoresponse of this device is tailorable, and most significantly, can be extended into the long-wavelength infrared regime by varying the Ge ratio x in the Si1-xGex layers. Results are obtained with x=0.2, 0.28, 0.3, and 0.4 on patterned Si (100) substrates. Photoresponse at wavelengths ranging from 2 to 10 μm is obtained with quantum efficiencies above ∼1% in these nonoptimized structures.