HIGH-TEMPERATURE DC CHARACTERISTICS OF ALXGA0.52-XIN0.48P GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS GROWN BY METAL-ORGANIC VAPOR-PHASE EPITAXY/

A series of AlxGa0.52-xIn0.48 P/GaAs heterojunction bipolar transistor s (HBT's) with x = 0 to x = 0.52 showed ideality factors close to unit y for both base current and collector current and small variation in g ain with temperature up to at least T = 623 K across the whole range o f a composition, Hole current injection from the base into the emitter in these devices was shown to be negligible, The current gain, beta, which is temperature insensitive was thought to be limited by bulk bas e recombination for x less than or equal to 0.3 and recombination at t he graded emitter region for x > 0.3. The optimum emitter composition (highest beta, and good beta stability with collector current and temp erature) was found to be x = 0.18-0.30, Useful transistor action with very high gain and output resistance is possible up to at least T = 62 3 K, limited only by the thermal performance of the unoptimized ohmic contacts employed in the devices.