A COMPARISON OF TMGA AND TEGA FOR LOW-TEMPERATURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH OF CCL4-DOPED INGAAS

Factors which influence the alloy composition and doping level of CCl4-doped In0.53Ga0.47As grown at low temperatures (450-degrees-C < T(g) < 560-degrees-C) by low-pressure metalorganic chemical vapor deposition (MOCVD) have been investigated. The composition is highly dependent on substrate temperature due to the preferential etching of In from the surface during growth and the temperature-dependent growth efficiency associated with the Ga source. The lower pyrolysis temperature of TEGa relative to TMGa allows the growth of CCl4-doped InGaAs at lower growth temperatures than can be achieved using TMGa, and results in improved uniformity. High p-type doping (p approximately 7 x 10(19) cm-3) has been achieved in C-doped InGaAs grown at T(g) = 450-degrees-C. Secondary ion mass spectrometry analysis of a C-doping spike in InGaAs before and after annealing at approximately 670-degrees-C suggests that the diffusivity of C is significantly lower than for Zn in InGaAs. The bole mobilities and electron diffusion lengths in p+-InGaAs doped with C are also found to be comparable to those for Be and Zn-doped InGaAs, although it is also found that layers which are highly passivated by hydrogen suffer a degradation in hole mobility. InP/InGaAs heterojunction bipolar transistors (HBTs) with a C-doped base exhibit high-frequency performance (f(t) = 62 GHz, f(max) = 42 GHz) comparable to the best reported results for MOCVD-grown InP-based HBTs. These results demonstrate that in spite of the drawbacks related to compositional nonuniformity and hydrogen passivation in CCl4-doped InGaAs grown by MOCVD, the use of C as a stable p-type dopant and as an alternative to Be and Zn in InP/InGaAs HBTs appears promising.