Heterojunction bipolar transistor

[3] Kroemer was awarded a Nobel Prize in 2000 for his work in this field at the University of California, Santa Barbara.

Due to the need to manufacture HBT devices with extremely high-doped thin base layers, molecular beam epitaxy is principally employed.

IBM and others use ultra-high vacuum chemical vapor deposition (UHVCVD) for SiGe; other techniques used include MOVPE for III-V systems.

[4][5] Besides being record breakers in terms of speed, HBTs made of InP/InGaAs are ideal for monolithic optoelectronic integrated circuits.

The bandgap of InGaAs works well for detecting 1550 nm-wavelength infrared laser signals used in optical communication systems.

Bands in graded heterojunction npn bipolar transistor. Barriers indicated for electrons to move from emitter to base, and for holes to be injected backward from base to emitter; Also, grading of bandgap in base assists electron transport in base region; Light colors indicate depleted regions .