Intrinsic Luminescence of GaAs/AIGaAs Heterojunctions in a Transverse Electric Field
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INTRINSIC LUMINESCENCE OF GaAs/AIGaAs HETEROJUNCTIONS IN A TRANSVERSE ELECTRIC FIELD Q.X. ZHAO, J.P. BERGMAN, P.O. HOLTZ, B. MONEMAR, and C. HALLIN Department of Physics and Measurement Technology, Linkoping University, S-581 83 Linkoping, Sweden M.SUNDARAM, J. L. MERZ and A.C. GOSSARD Department of Electrical and Computer Engineering and Materials Department, University of California, Santa Barbara, California 93106, USA
ABSTRACT Radiative recombination of the two dimensional electron gas (2DEG) in a modulation doped GaAs/AIGaAs heterojunction (the so called H-band luminescence) has been studied under transverse electric field perturbation (i.e. perpendicular to the layers) in special structures prepared by molecular beam epitaxy. Both positive and negative gate voltages have been applied to the GaAs/AIGaAs interface, and shifts of the H-band energy position depending on the gate voltage are induced by the corresponding changes in the notch potential and the potential across the GaAs layer. It is demonstrated that a transverse electric field allows a simple way to modify the width and shape of the potential, so that detailed spectroscopy can be done on the recombination of carriers localized in a interface potential. INTRODUCTION During the last decade there has been a considerable interest in the electronic properties of two-dimensional (2D) systems [1]. With the recent developments of epitaxial growth techniques a good quality 2D interface between GaAs and AIGaAs can be achieved. A large number of experimental studies have been carried out on GaAs/AIGaAs heterostructures using various electrical techniques, while our knowledge about the optical properties is much more limited. Photoluminescence (PL) studies of the so called H-band, which is due to radiative recombination involving carriers confined in the GaAs/AIGaAs interface potential, have been presented for samples grown by different techniques, such as liquid phase epitaxy (LPE) [2], molecular beam epitaxy (MBE) [3,4,5,6], and metalorganic chemical vapor deposition (MOCVD) [7]. To our knowledge, no detailed work has previously been published on the electronic properties of carriers localized at the GaAs/AIGaAs hetero-interface, where electrical and optical methods have been combined. Mat. Res. Soc. Symp. Proc. Vol. 163. ©1990 Materials Research Society
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In this presentation, we report the first results on the optical properties of the PL H-band with an electric field as a perturbation. The experimental results show that the energy position of the H-band depends on the external applied gate voltage. For positive and negative gate voltages the energy position of the H-band shifts in opposite directions, which has to be explained by the change of the potential at and close to the interface caused by a electric field. The dependence of the H-band on the excitation power and the temperature has also been studied for different gate voltages. The results of this work are consistent with a model of the H-band as due to the radiative recombination of the 2DEG
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