Transient acoustoelectric spectroscopy measurements for the characterization of GaAs epilayer structures

Abstract

A new measurement technigue, acoustoelectric deep-level transient spectroscopy (AE-DLTS) is used to characterize the GaAs epilayer film grown on a semi-insulating GaAs substrate. The electric field. generated by the propagation of a surfaceacoustic wave fsnw)onapiezoelectriccrystai, is used asaprobing tool to studythe transient behaviour ofdeep levels. This field interacts with the freecarriers present in the semiconductor, resulting in an alteration of the carrier density at the surfaceofthesemiconductor and the generation of aocvoltage.The rateatwhich excess charges are induced at the semiconductor surface, or diminished after the passageofthes~wpulse, is related tothe positionand thecrosssectionofthedeep levels at the interface between the epilayer and the substrate. The theoretical analysis ofthefall timeoftheocvoltage ispresented along withexperimental verification. In our experiments the voltage transients were recorded as afunction of incident photon energy and at differenttemperatures, and the thermal and optical cross sections of the EL2 level in GaAs were evaluated from computer fit.

Defect engineering using microwave processing in SiC and GaAs

“…The primary process, which determines defect production under irradiation, is a displacement of the atoms from the sites of the lattice. But the energy of a photon with frequency 2.45 GHz is about 10 −5 eV only; the threshold displacement energies in GaAs and SiC are (8-28) eV [74] and (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) eV [75], respectively. Therefore such a channel of microwave-induced modification of defect subsystem is unreal.…”

“…It is believed [28][29][30] that the TAV that arises in epitaxial structures is mostly caused by defects located at the epi-layer and substrate interface. In addition, the growth of epitaxial layers is known to lead to the arising of redundant dislocations at the interface.…”

“…The parameters of defects, such as the capture cross section of electron σ n and the energy level with respect to the conductivity band bottom (E c − E t ) were determined both before and after MWT. For this purpose, we used acoustoelectric transient spectroscopy [28][29][30][31]. The principle of this spectroscopy closely coincides with the idea of the DLTS technique [32], but the barrier formation is not required, and defects at the epi-structure interface can be detected [28][29][30].…”

“…For this purpose, we used acoustoelectric transient spectroscopy [28][29][30][31]. The principle of this spectroscopy closely coincides with the idea of the DLTS technique [32], but the barrier formation is not required, and defects at the epi-structure interface can be detected [28][29][30]. A schematic representation of method is shown in figure 2.…”

“…A simple exponential dependence according to equation ( 1) is observed in cases where only one type of trap is effective in acoustoelectric interactions. For n-type semiconductors, the characteristic relaxation time is described by the equation [28,30]:…”