Micro Raman study of dislocations in n‐type doped GaAs

Abstract

Micro Raman spectroscopy was used in order to clarify dislocation-related effects in a GaAs sample Bridgemangrown from a slightly As-rich melt and doped with Si to achieve a free electron concentration of about 10'* c~n -~. The specific advantage of the Raman method is demonstrated by the direct observation of an increase in the carrier concentration in the vicinity of dislocations and by the detection of both crystalline and amorphous As in the dislocation core. A defect model is proposed, which is in agreement with results obtained by other methods such as high spatial resolution photoluminescence. The possibility of determining internal lattice distortions by means of Raman spectroscopy is discussed, but further systematic investigations are necessary to obtain reliable results.

Influence of dislocation content on the quantitative determination of the doping level distribution in n-GaAs using absorption mapping

“…Theoretical calculations confirm the experimental results [10]. Typical doping levels where Si acceptors, Si clusters and Si Ga -Ga-vacancy complexes are formed are given in [4] 15], phase contrast microscopy [15] and Micro-Raman analysis [13][14][15]. The various results show that in the case of Si doping the defect atmosphere is characterized by an increase, in the case of Te doping by a decrease of the charge carrier concentration compared to the surrounding material.…”

“…Interstitials move to the dislocation and replace the dopant atom on a substitutional site in the As-sublattice. The dopant now occupying the interstitial position becomes a fast diffuser [13].…”

Impact of Individual Structural Defects in GaAs Solar Cells: A Correlative and In Operando Investigation of Signatures, Structures, and Effects

“…These findings explain why the phonon frequency shift observed at the defective region, presumably associated with the defect induced strain, tends to be larger than that expected for a simple dislocation. [ 32 ] Although we did not observe significant change of the TO mode intensity at the defect site, as one would have expected resulting from relaxation in selection rule due to defect induced disordering, [ 19,20 ] we do observe a strongly enhanced TO Raman mode at the location of the pit, as shown in Figure 6a, which has {111} like surfaces for which TO Raman scattering is allowed.…”

“…Although a simple dislocation defect may induce local strain, the effects are expected to be relatively weak: a less than 0.1 cm −1 shift of the LO model frequency. [ 32 ] Dislocations were reported to relax the TO selection rule (forbidden for (001) backscattering), [ 19,20 ] but this effect is minimal for the dislocation defects studied here, as evident in Figure 3e. These discrepancies are discussed later.…”

“…There were early attempts at correlative studies of dislocation defects in GaAs ingots using Raman, photoluminescence (PL), electron-beam-induced current (EBIC), and transmission electron microscopy (TEM), but the defects in the ingots exhibited rather different behavior than in epitaxial layers, and the studies were performed with low spatial resolution. [19,20] Recently, we made a concentrated attempt to correlate PL imaging/chemical etching/scanning electron microscopy (SEM) imaging in CdTe epilayers, and found that etch pits, which are the result of the classical defect study approach of chemical etching, did not always match the dark spots visible in PL imaging. [12] Although the results of the PL imaging were somewhat better at reflecting the impact of defects in real devices, the PL process still did not reveal how the carriers were generated, injected, or extracted in real electronic or optoelectronic devices, such as transistors, photodetectors, solar cells, and LEDs.…”