Simulation de l’effet de la température et les défauts sur les caractéristiques électriques des diodes à base de GaAs (Simulation of the temperature and the deep traps effect on the electrical characteristics of GaAs diodes)

Abstract

The capacitance-voltage (C-V) characteristic is one of the most important characteristic which used to evaluate the quality of semiconductors. It is a non-destructive method of characterization and it gives an insight into the devices (structural and electrical information). Deep Level Transient Spectroscopy (DLTS) is another technique frequently used to characterize defects in semiconductors. In this work two silicon-doped p-type Gallium Arsenide (GaAs) samples were grown by Molecular Beam Epitaxy on (211)A and (311)A oriented GaAs semi-insulating substrates to form Schottky diodes. (211) and (311) indicate the crystallographic orientation of the substrate while the letter A indicates a Ga-terminated surface. They are investigated using C–V measurements at different temperatures and DLTS. These samples showed a strange behaviour of capacitance-voltage and capacitance-temperature characteristics. The C-V characteristics of the (311)A sample showed a negative differential capacitance (NDC) while those of the (211)A sample showed a smaller than usual sensibility to voltage. DLTS revealed the existence of different types of defects in the two samples. In the (311)A structure only majority deep levels (hole traps) were observed while both majority and minority deep levels were present in the (211)A sample. In order to relate this behaviour to the observed deep levels, a thorough numerical simulation using the SILVACO-TCAD software is carried out to simulate the C–V and the C-T characteristics in the absence and presence of different types of deep levels. It was found that a non-uniform distribution of one of the deep acceptors is responsible for the NDC phenomena in the (311)A sample while the non-sensitivity of the capacitance to voltage is related to compensation between deep acceptors and deep donors in the (211)A sample.