The Effect on Turn-On Voltage (VBE) of AlGaAs/GaAs HBT's due to the Structure of the Emitter-Base Heterojunction

Abstract
The effects on the turn-on voltage (VBE) of collector current in AlGaAs/GaAs HBT's due to Be diffusion and discontinuity in the conduction band are investigated. It is clarified that V BE increases significantly with the decrease in saturation current due to Be diffusion into the AlGaAs emitter during MBE growth. It is also found that the V BE's of HBT's with Al compositionally abrupt and graded emitter-base junctions and homojunction GaAs bipolar transistors are the same. These results indicate that the spike-like potential barrier at the heterojunction has no influence on the electron injection from emitter to base.