InGaAs/InP heterojunction bipolar transistors grown with gas source molecular beam epitaxy

The effects of emitter-base doping and base setback layers on recombination, emitter efficiency, and gain of InGaAs/InP heterojunction bipolar phototransistors (HPTs) were studied experimentally. Six different HPT designs were investigated; three had setback layers and three did not. All of the HPTs were fabricated from gas source MBE (molecular-beam epitaxy)-grown lattice-matched InGaAs/InP layers which were chemically etched into square mesas 380 mu m on a side. The wafers with no setback layer and high emitter-base doping produced HPTs with maximum gains only in the 50-200 range. Theoretical analysis suggests that the large variation in gain with different layer dopings and setbacks is strongly influenced by the location and width of the energy notch caused by the conduction band offset.<
>