InP-based single heterojunction bipolar transistors with improved breakdown characteristics

InP-based heterojunction bipolar transistors (HBTs) have been fabricated from material grown by metal organic molecular beam epitaxy (MOMBE) using InGaAsP with a bandgap of 0.95 eV as both the collector and base material. The 400 Å collector was undoped with an electron concentration of 6×10¹⁶ cm^-3 and the 850 Å base layer was doped with Mg to a hole concentration of 10¹⁹ cm^-3. The DC current gain of a large area (90 μm diameter) device was measured to be 340 with a base sheet resistance of 760 Ω/□. The collector and base ideality factors were 1.1 and 1.4, respectively. The breakdown voltage V_CEO of 7.5 V represents a significant improvement over similar devices with conventional InGaAs collector and base layers