A study was made of the effect of structural defects upon spatial variations in radiative and non-radiative recombination, in a resonant cavity enhanced npn heterojunction structure, using cathodoluminescence and electron beam-induced current imaging. The current gain of the structure under an applied bias voltage depended upon the hole accumulation efficiency in the base, and therefore upon the hole lifetime. Strain relaxation-induced misfit dislocations in the multiple quantum wells were found to create regions of enhanced non-radiative recombination; thereby locally reducing the hole accumulation efficiency and current gain. The reduction in the local electron beam-induced current signal which was caused by dark-line defects was less than about 20%. This suggested that misfit dislocations in this structure had a relatively small effect upon overall device performance. The temperature dependences of the electron beam-induced current and spectrally integrated cathodoluminescence images were studied at 85 to 300K, and this revealed that non-radiative recombination in the vicinity of misfit dislocations was mainly thermally activated, with spatial variations in lifetime and activation energy.

H.T.Lin, D.H.Rich, O.Sjölund, M.Ghisoni, A.Larsson: Journal of Applied Physics, 1996, 79[10], 8015-23