Hot-electron injection in AlGaSb/GaSb HBT-its relation to the conduction band structure of GaSb

The authors report on hot-electron injection in the AlGaSb/GaSb heterojunction bipolar transistor (HBT). It is revealed that the current gain is strongly dependent on conduction band discontinuity at the emitter-base junction. This is discussed in relation to the hot-electron injection and the conduction band structure of GaSb base material. The current gain ( beta ) measured at room temperature was found to increase monotonically from 8 (y/sub 0/=0) to as high as 160 (y/sub 0/=0.5). An increase in beta up to y/sub 0/=0.5 can be interpreted as an increased initial velocity due to electron injection with large kinetic energy into the L-band of the base. The use of the y/sub 0/ equivalent to 0.5 emitter has been shown to provide high beta and short transit time in the base AlGaSb/GaSb HBT structure.