A novel InGaP/AlxGa1-xAs/GaAs CEHBT

A new and interesting InGaP/AlxGa1-xAs/GaAs composite-emitter heterojunction bipolar transistor (CEHBT) is fabricated and studied. Based on the insertion of a compositionally linear graded AlxGa1-xAs layer, a near-continuous conduction band structure between the InGaP emitter and the GaAs base is developed. Simulation, results reveal that a potential spike at the emitter/base heterointerface is completely eliminated. Experimental results show that the CEHBT exhibits good de performances with dc current gain of 280 and greater than unity at collector current densities of J(C) = 21 kA/cm(2) and 2.70 x 10(-5) A/cm(2), respectively. A small collector/emitter offset voltage AVCF, of 80 meV is also obtained. The studied CEHBT exhibits transistor action under an extremely low collector current density (2.7 x 10(-5) A/cm(2)) and useful current gains over nine decades of magnitude of collector current density. In microwave characteristics, the unity current gain cutoff frequency f(T) = 43.2 GHz and the maximum oscillation frequency f(max) = 35.1 GHz are achieved for a 3 x 20 mu m(2) device. Consequently, the studied device shows promise for low supply voltage and low-power circuit applications.