Self-aligned In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistors with graded interface on semi-insulating InP grown by molecular beam epitaxy

A self aligned In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As double heterojunction bipolar transistor (HBT) with a graded heterointerface has been grown by molecular-beam epitaxy (MBE) and tested. The DC characteristics of HBT structures with a compositionally graded junction using a linear graded In/sub 0.53/Ga/sub 0.47-x/Al/sub x/As between two ternary layers were investigated. Typical quaternary graded devices with an emitter dimension of 50*50 mu m/sup 2/ exhibited a current gain as high as 1260, as compared to 800 for abrupt devices, at a collector current density of 2.8*10/sup 3/ A/cm/sup 2/.<
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