Effect of Doping on the Interface States in Au Schottky Contact to p-In 0.21 Ga 0.79 As Grown on GaAs by Metal Organic V
- PDF / 342,662 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 66 Downloads / 175 Views
**
P. COVA* and R. A. MASUT**
Universidad de Oriente, Departamento de Fisica, Laboratorio de semiconductores, Apartado 188, CumanA, 6101, Sucre, Venezuela Ecole Polytechnique de Montr6al, Ddpartement de gdnie physique, P.O. Box 6079, Station "Centre-Ville", Montrdal (Qudbec), H3C 3A7, Canada
ABSTRACT Epitaxial p-In0 .21Ga 0.79As/Au Schottky barrier type diodes were fabricated by evaporation of Au on chemically etched surfaces of In0 21Ga 0.79As:Zn layers grown on highly doped GaAs substrate by MOVPE. 1 MHz capacitance-voltage (C-V) and Capacitance-frequency (C-f) measurements were performed in the frequency range 1 KHz- 1 MHz at room temperature in Au Schottky diodes made on four epitaxial p-In0* 2 Ga 0 79As:Zn samples with doping concentrations between 6x10"4 cm-' and 4x10 17 cm 3 . Under forward bias, a large frequency dispersion in the junction capacitance was observed which was attributed to the interface states in thermal equilibrium with the semiconductor. The interface states capacitance extracted from the C-f data was analyzed in terms of Lehovec's theoretical model of interface state continuum with single time constant, and the characteristic parameters of the interface states (energy density (N,,), relaxation time (t) and hole capture cross-section (Oh)) were determined. In the samples with doping concentration in the range 1.5x10 17 -4.3x10 17 cm-', N,, was about an order of magnitude higher than in the sample having a doping concentration of 5.8x10 14 cm-3. Over the interface states energy range 0.40-0.65 eV, N,, decreased exponentially with energy in the highly doped samples and 0 h increased with energy in all the samples. INTRODUCTION Heteroepitaxial ternay alloy semiconductor layers such as InGaAs/GaAs are of interest for the fabrication of devices, mostly as strained-layer heterostructures [1-4]. Relatively thick, relaxed, layers are also of technological interest [5]. In thick layers, defects are created during growth due to mismatch which depend on substrate orientation [6] and impurity incorporation. Such relaxed structures can be of good crystalline quality and are used to study the effect of growth parameters on the properties of these materials. Here we have looked at the effect of doping concentration on the characteristic parameters of the surface states in thick (-3 gim) heteroepitaxial layers of In 021Ga. 79As doped with Zn during growth. The layers were grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on highly doped GaAs substrate. We have used Au Schottky contacts as a tool to determine the effect of doping impurities on the parameters of the surface states. We have investigated the diodes fabricated simultaneously using the same metal Schottky contact to p-In0 21Ga0 .79As epitaxial layers, differing in doping concentration by three orders of magnitude.
513 Mat. Res. Soc. Symp. Proc. Vol. 318. ©1994 Materials Research Society
EXPERIMENTAL TECHNIQUE Four epitaxial p-In0 .21Ga0. 79As samples (MoO0, Mo09, Mol3 and Mol4) approximately 3 um thick with different doping concentrations
Data Loading...
