Raman scattering of residual acceptors in GaAs and its application to optical topography: Chapter 6

Raman scattering of acceptors in GaAs is discussed. It is shown how this technique can be used for a quantitative assessment of residual acceptors in semi-insulating material. Based on this quantitative assessment it is further demonstrated that Raman scattering allows on optical topography of the residual acceptor distribution in GaAs wafers. (IAF

Nondestructive topographic evaluation of ion implanted layers on GaAs substrates by optical absorption.

It is demonstrated that ion implanted layers can be analysed prior to annealing by measuring the sub-bandgap optical absorption of the damaged lattice. The absolute value and lateral homogeneity of the implantation dose can be measured. The method is fast, nondestructive and compares favorably with existing measurement techniques. (IAF

Contactless evaluation of semi-insulating GaAs wafer resistivity using the time-dependent measurement.

A method based on time-dependent measurement of charge transients has been developed to evaluate the specific resistivity of semi-insulating wafers quickly, non- destructively and with good lateral resolution. The material is inserted between capacitive electrodes. The time-dependent charge distribution after application of a voltage step allows evaluation of the resistivity with high accuracy in the range 10high6- 10high9Omegacm. The technique has been elaborated to allow rapid contactless scanning of wafers for routine measurement of the lateral variation of resistivity with a resolution of about 2 mmhigh2. The results are in agreement with conventional Hall measurements. The mechanical and electronic systems are described in detail. Scans across wafers cut from as-grown as well as annealed ingots are presented

New photosensitive EPR signals in undoped semi-insulating GaAs

Three new EPR signals labelled FR1, FR2 and FR3 have been observed in undoped as grown LEC GaAs. They are well observable only below 10K, their intensities are high and they appear only after optical excitation. Thus the defects involved are electrically active and occur in high concentrations. Tentative models for the three centers are presented. (IAF