InGaP/InGaAsN/GaAs NpN double-heterojunction bipolar transistor

We have demonstrated a functional NpN double-heterojunction bipolar transis tor (DHBT) using InGaAsN for the base layer. The InGaP/In0.03Ga0.97As0.99N0 .01/GaAs DHBT has a low V-ON of 0.81 V, which is 0.13 V lower than in a InG aP/GaAs heterojunction bipolar transistor (HBT). The lower turn-on voltage is attributed to the smaller band gap (1.20 eV) of metalorganic chemical va por deposition-grown In0.03Ga0.97As0.99N0.01 base layer. GaAs is used for t he collector; thus the breakdown voltage (BVCEO) is 10 V, consistent with t he BVCEO of InGaP/GaAs HBTs of comparable collector thickness and doping le vel. To alleviate the current blocking phenomenon caused by the larger cond uction band discontinuity between InGaAsN and GaAs, a graded InGaAs layer w ith delta doping is inserted at the base-collector junction. The improved d evice has a peak current gain of seven with ideal current-voltage character istics. (C) 2000 American Institute of Physics. [S0003-6951(00)02116-1].