(In,Ga)As/(In,Al)As heterojunction lateral PNP transistors

We report the first (In,Ga)As/(In,Al)As heterojunction lateral PNP transistors. These devices were developed for use as the current source injectors in (In,Ga)As integrated injection logic, a potentially very high speed, high density, lower power III-V bipolar logic family. The PNP transistors are fabricated in an n-type (In,Ga)As/ (In,Al)As heterostructure grown by molecular beam epitaxy on an n⁺-InP substrate. P-type emitter and collector regions are formed by Be⁺implantation. The parasitic, vertically injecting emitter-base junction is formed in the wider band-gap (In,Al)As region while the active, laterally injecting emitter-base junction is formed in the narrower band-gap (In,Ga)As. The saturation current densities of these junctions are found to differ by over three orders of magnitude. A transistor current gain of 3.8 is obtained for collector currents from 10µA to 200µA in devices with a pattern base width of 3µm and an electrical base width of 1.5µm.