Investigation of the negative peak in photoinduced transient spectra of semi-insulating gallium arsenide

Abstract

The interpretation of ohmic behavior in semiinsulating gallium arsenide systems A common observation in the photoinduced transient (PITS) spectra of semi-insulating GaAs is the appearance of a negative peak, which is anomalous in that both electron and hole traps should give rise to positive peaks, In this paper, it is shown that the negative peak can be explained in terms of charge exchange with the GaAs surface and only occurs in material which displays particular types of current-voltage and current-temperature characteristics. The dependence of this peak on the processing effects of surface passivation, etching, and baking and polishing has been investigated and its sensitivity to variations in incident light intensity is demonstrated. A new variation of PITS, namely gated-PITS has been employed. This technique suppresses the negative peak in the spectrum, allowing transients corresponding to emission from EL2 to be detected in particular undoped liquid encapsulated Czochralski GaAs substrates for the first time. 215 J.

Identification of deep defects in high-resistivity undoped LEC-GaAs irradiated with protons

“…At high temperatures (T > 340 K), a strong negative peak is observed. This peak has been reported in the literature [12], and was attributed to a charge exchange mechanism occurring between the bulk and the surface of the material. In the irradiated samples, in addition to the peaks T1-T5, there is a new positive peak T6 located at room temperature with an apparent activation energy of 0.72 eV.…”

Explanation of positive and negative PICTS peaks in SI-GaAs

“…In contrast to low temperature studies of GaAs [11,13] (e.g. simulations of the EL2 photoquenching effect), where equilibrium occupations of the bands are practically zero and can be neglected, they are important for the simulation of negative peaks for temperatures above 300 K, where transients are known to show a drop below equilibrium values [6].…”

“…N EL2 = 1.56 9 10 16 cm -3 , N RC = 1 9 10 14 cm -3 J Mater Sci: Mater Electron calculated the PICTS signal from the simulated conductivity change Dr ¼ e 0 ðl n Dn þ l p DpÞ using a mobility ratio [17] of l n /l p = 20/1. As in the experimental investigation, a carrier generation (light pulse) time of 1 ms was used and PICTS data evaluation of the conductivity transients (signal after light cut-off) by a double-box-car technique [6,18] with an initial time delay t 1 C 10 ls was applied.…”

“…Especially in semi-insulating GaAs (SI-GaAs) positive and negative PICTS peaks, which are mostly attributed to the EL2 defect, can be observed at temperatures above &350 K, whereas the exact peak maximum temperature depends on the details of the applied PICTS data evaluation. The origin of this negative PICTS signal was addressed several times, but so far not clarified completely [4][5][6][7][8]. Essentially, most explanations involve a single deep level (usually the EL2), which interacts with both bands.…”

Photo-induced current spectroscopy study on semi-insulating LEC GaAs

“…At high temperature (T > 340 K), a strong negative peak is observed. Several authors [9,10] have studied this peak and attributed it to a charge exchange between the material bulk and surface. Figure 1(b) presents the planar mode related PICTS spectrum.…”