Carbon doping of compound semiconductor epitaxial layers using carbon tetrachloride

H2 has been used as a carbon dopant source for AlxGa1-xAs grown by low pressure metalorganic chemical vapor deposition (MOCVD). To understand the mechanism for carbon incorporation from CC14 doping, and to provide experimental parameters for the growth of carbon doped device structures, the effect of various crystal growth parameters on CC14 doping have been studied, including growth temperature, growth rate, V/VIII ratio, Al composition, and CC14 flow rate. Although CC14 is an effective p-type dopant for MOCVD AlxGa1-xAs, injection of CC14 into the reactor during growth of InP resulted in no change in the carrier concentration or carbon concentration from undoped InP layers. Abrupt, heavy carbon doping spikes in GaAs have been obtained using CC14 without a dopant memory effect. By annealing samples with carbon doping spikes grown within undoped, n-type, and p-type GaAs, the carbon diffusion coefficient in GaAs at 825 C has been estimated and has been found to depend strongly on the GaAs background doping. CC14 doping has been used in the base region of an Npn AlGaAs/GaAs heterojunction bipolar transistor (HPT). HPTs with 3 x 10 m self-aligned emitter fingers have been fabricated which exhibit a current gain cutoff frequency of ft = 26 GHz.