Capacitance Spectroscopy of Single-Barrier GaAs/AlAs/GaAS Structures Containing InAs Quantum Dots

Abstract

In this paper we investigate the capacitance-voltage, 0(V), and magneto-capacitance, 0(B), characteristics of a series of single-barrier ni-n GaAs/AlAs/GaAs heterostructures incorporating a layer of self-assembled InAs quantum dots (QDs) in the AlAs barriex. Thicknesses of the layers of AlAs deposited before and after the InAs QD growth are varied. The C(V) and C(B) results are compared with those from a control sample that has no InAs and a sample in which the InAs thickness is such that a continuous wetting layer (WL) of InAs is grown. The samples presented in this study were grown on a (100) n+-GaAs substrate using MBE and all consist of n-type GaAs devices with an AlAs tunnel barrier region surrounded by 100 nm not intentionally doped spacer8 to minimise the effect of dopant diffusion into the central barrier region. These spacers are then enclosed by 100 nm of n-type GaAs doped to a density of 10 16 cm -3 lightly doped region, followed by 100 nm doped to 10 17 cm-3 , and then a heavily doped contact layer, at 10 18 cm -3 . The control sample consists of a 10 nm AlAs single barrier, while the WL sample consists of an AlAs double barrier structure enclosing 1.4 ML of InΑs. The QD samples consist of a InAs QD layer enclosed in AlAs layers grown previously and subsequently to the QD growth. The QDs are produced by deposition of 1.8 ML of InAs at a growth temperature of 520°C. The detailed layer make-up of the samples presented in this work are shown in Table. The band diagram of the samples at zero voltage and under applied bias is drawn schematically in Fig. 1. Electrical contacts were formed on the doped GaAs