Evidence for surface recombination at mesa sidewalls of self-electro-optic effect devices

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Abstract
We measured the forward current-voltage characteristics of self-electro-optic effect devices (SEED). These devices consist of p-i-n diodes where the i region is a GaAs/AlxGa1−xAs (x∼0.3) multiple-quantum-well structure. It is found that the diode current varies as exp(qV/2 kT) and that it also scales with the junction perimeter for diodes of different mesa sizes, indicating nonradiative surface recombination at the mesa sidewalls. We also measured minority-carrier lifetimes from photoluminescence decay experiments. They revealed that the recombination rate increases with decreasing mesa size, once again indicating that surface recombination at the mesa sidewalls limits carrier lifetime. A value of 6×105 cm s−1 for the surface recombination velocity for the sidewalls is determined. The implication of the nonradiative surface recombination at the mesa sidewalls is that it undermines the performance of the SEED as the mesa size decreases by reducing the photocurrent, thereby leading to higher bistability voltage threshold and hence higher switching energy.