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 depositio n (MOCVD) have been investigated. The composition is highly dependent on substrate temperature due to the preferential etching of In from th e surface during growth and the temperature-dependent growth efficienc y associated with the Ga source. The lower pyrolysis temperature of TE Ga relative to TMGa allows the growth of CCl4-doped InGaAs at lower gr owth temperatures than can be achieved using TMGa, and results in impr oved 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. Sec ondary ion mass spectrometry analysis of a C-doping spike in InGaAs be fore 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 wit h C are also found to be comparable to those for Be and Zn-doped InGaA s, although it is also found that layers which are highly passivated b y hydrogen suffer a degradation in hole mobility. InP/InGaAs heterojun ction bipolar transistors (HBTs) with a C-doped base exhibit high-freq uency performance (f(t) = 62 GHz, f(max) = 42 GHz) comparable to the b est reported results for MOCVD-grown InP-based HBTs. These results dem onstrate that in spite of the drawbacks related to compositional nonun iformity 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 an d Zn in InP/InGaAs HBTs appears promising.