Cm. Colomb et al., ZERO-FIELD TIME-OF-FLIGHT CHARACTERIZATION OF MINORITY-CARRIER TRANSPORT IN HEAVILY CARBON-DOPED GAAS, Journal of applied physics, 73(11), 1993, pp. 7471-7477
Minority-carrier electron-diffusion coefficients and lifetimes have be
en measured in heavily doped p-type GaAs using the zero-field time-of-
flight (ZFTOF) technique. The materials studied included C-doped GaAs
grown by molecular-beam epitaxy (MBE) using graphite as the dopant sou
rce, C-doped GaAs grown by metalorganic chemical-vapor deposition (MOC
VD) using CCl4 as the dopant source, and Be-doped GaAs grown by MBE. R
oom-temperature photoluminescence intensity measurements were made on
the structures and the results are compared with ZFTOF measurements of
lifetime. The graphite-doped material (p approximately 10(19) CM-3) e
xhibited diffusion lengths of less than 1000 angstrom. MOCVD-grown C-d
oped GaAs, which was optimized by adjusting the growth conditions to m
aximize the room-temperature photoluminescence intensity, had diffusio
n lengths comparable to those measured in Be-doped GaAs for hole conce
ntrations of 1 X 10(19) and 5 X 10(19) CM-3. Comparison of photolumine
scence intensities also suggests that addition of In to very heavily d
oped MOCVD-grown GaAs (p > 10(20) cm-3) to eliminate the lattice misma
tch with respect to the substrate does not result in an improvement in
lifetime.