Surface damage, semiconductors

Fig. 92. Spectral distribution of the electroluminescence of four semiconductors in 5 M NaOH/ 0.05 M Na2S208. The dotted curve for n-ZnO corresponds to the case of considerable surface damage.

Other phenomena which have been observed on damaged semiconductor surfaces include the following. Ahearn and Law (27) have studied the Russel effect, the darkening of a photo-... 

The presence of high dislocation densities in damaged semiconductor surfaces has been suggested (13,28,29, 23) but no direct evidence has been reported. Faust (13) has pointed out a difficulty in considering dislocations, which is that they are ordinarily produced by deformation at elevated temperatures. 

Surface Anatysis. Surface analysis can be employed in many situations, but it is particularly well suited for the analysis of contamination or surface damage. In many industries, contamination at the nanometer scale can spell disaster for a process. For example, semiconductor materials have very predictable conductive behavior, which is essential for designing microelectronics that work properly. The addition of contaminants to the system will change the behavior of the materials and can cause failures, so it is essential that surface analysis be employed in the development of a product and sometimes during manufacturing stages to ensure that the materials are clean and reliable. 

Surface reconstructions are common in both metal surfaces and semiconductor surfaces. The driving force behind the reconstruction is the need of the system to repair the damage done by the introduction of the surface, which severs the bonds of atoms on the exposed plane. 

Etch Mechanisms. Most wet etches for the compound semiconductors employ oxidation of the semiconductor followed by dissolution of the oxide. For this reason, many wet etches contain the oxidant hydrogen peroxide, although nitric acid can also be used. One advantage of wet etching over dry is the absence of subsurface damage that is common with dry etching. Metal contacts placed on wet-etched surfaces exhibit more ideal characteristics than dry-etched surfaces. 

---