Interface properties of isotype GaAs/(In,Ga)P/GaAs heterojunctions grown by metalorganic-vapour-phase epitaxy on GaAs

Abstract

Metal-semiconductor contacts are used to examine the depth-resolved electrical characteristics of Si- and Zn-doped GaAs/(In,Ga)P/GaAs heterojunctions by capacitance–voltage measurements and deep-level transient Fourier spectroscopy. The experimental depth profiles of the carrier concentration are compared with calculations based on self-consistent solutions of the Poisson equation. By varying the growth conditions, heterointerfaces of GaAs with disordered or double- and single-variant ordered (In,Ga)P layers are produced. It is shown that normal [(In,Ga)P-on-GaAs] and inverted [GaAs-on-(In,Ga)P] interfaces are not equivalent with respect to their electrical properties. For the inverted Si-doped heterointerface, the depth profiles of the electron concentration strongly depend on the growth conditions. In spite of a large carrier deficit at this interface, the density of interfacial traps in the upper half of the bandgap is found to be low in the 10 9 cm −2 range. For interfaces with disordered (In,Ga)P, the conduction and valence band offsets are independently determined to be 0.20 and 0.27 eV, respectively. These heterointerfaces exhibit type-I character, in agreement with theoretical predictions. For interfaces with single-variant ordered (In,Ga)P, the conduction band discontinuity is found to be also 0.20 eV, in contrast to calculations of the band alignment for ordered (In,Ga)P, which predict −0.13 eV.