Abstract

In a semiconductor doping or n-i-p-i superlattice, the periodic variation of impurities introduces a space-charge-induced superlattice potential which modifies the bulk electronic band structure and allows tailoring of the optical properties. We propose that short-period doping superlattices are suitable for the enhancement of a third- order optical susceptibility arising from electrons in nonparabolic conduction subbands. The advantages of doping superlattices are the ability to simply engineer the superlattice potential profile, thus giving control of miniband dispersion, and to provide free carriers to occupy these subbands. Room temperature electronic and nonlinear optical properties are calculated and optimized for uniformly doped and planar doped superlattice geometries. Compensated calculations are used to determine the superlattice potential profile which gives an optimally nonparabolic first conduction subband. We then self-consistently calculate the resulting optical nonlinearity for noncompensated n-type superlattices possessing this same potential shape. We show that small modulations of the superlattice potential lead to small minigaps and large subband nonparabolicities; a twentyfold improvement in the third-order optical susceptibility over bulk GaAs is predicted. Optical characterization and preliminary measurements for uniformly doped GaAs doping superlattices are discussed.

© 1989 Optical Society of America