We have systematically studied the influence of Si doping on the chara
cteristics of InGaN/GaN multiple quantum wells (MQWs) by means of high
-resolution x-ray diffraction (HRXRD), photoluminescence (PL), PL exci
tation (PLE), and time-resolved PL spectroscopy. The twelve period MQW
s were grown by metalorganic chemical vapor deposition. Si doping in t
he GaN barriers was varied from 1 X 10(17) to 3 X 10(19) cm(-1). Infor
mation on the structural quality of the MQWs as a function of Si dopin
g was extracted from the linewidth broadening of the higher-order supe
rlattice satellite peaks measured in HRXRD. The HRXRD measurements ind
icate that increased Si doping results in better interface properties
of the MQWs. PL and PLE measurements show a decrease in the Stokes shi
ft with increasing Si doping concentration. The 10 K radiative recombi
nation lifetime was observed to decrease from similar to 30 ns (for n
< 1 x 10(17) cm(-3)) to similar to 4 ns (for n = 3 x 10(19) cm(-3)) wi
th increasing Si doping concentration. The reduced Stokes shift, the d
ecrease in radiative recombination lifetime, and the increase in the i
nterface quality indicate that Si doping results in a decrease in carr
ier localization at potential fluctuations in the InGaN active layers.
(C) 1998 American Institute of Physics. [S0003-6951(98)00434-3]