Optical mapping of residual stress in Czochralski grown GaAs

Abstract

Despite several detailed theoretical analyses of the stress distribution expected for Czochralski grown GaAs crystals, experimental verification of these calculations has hitherto relied on dislocation density measurements. The present work shows that weak photoelastic patterns are resolvable in the near-infrared transmittance (typically near 1.4 μm) of semi-insulating GaAs wafers. Mapping of these patterns reveals the contours of constant shear stress, with results generally supporting the calculated models for the stress distribution.

Effect of polishing stress on Raman spectra of the Mn–Zn ferrite

“…Recently, Lutz et al 17 observed the Raman spectra of ZnCr 2 O 4 (T N ϭ13 K) and identified the symmetry coordinates associated with the five experimentally observed Raman spectra, as listed in Table III. This reference is confirmed by the fact that the Zn-O distance ͑ϭ1.97 Å͒ of the tetrahedral sites in ZnCr 2 O 4 18 is very close to the 1.98 Å in ZnFe 2 O 4 . 19 The E g and A 1g modes given in Table III Zn ions in the A sites.…”

“…The residual stress in semiconductive substrates such as Si and GaAs has been measured and investigated mainly by means of nondestructive methods such as photoelasticity, 1,2 x-ray topography, 3,4 photoluminescence, 5,6 and Raman spectroscopy. [7][8][9] The residual stress in soft magnetic substrates, however, has hitherto been evaluated using an ellipsometer 10 which provides information closely associated with the electronic transition from the ground state to the excited one.…”

“…1 mol % Fe 2 O 3 , 31.6 mol % MnO, and 15.3 mol % ZnO, which corresponds to the formula Mn 0.62 Zn 0.30 Fe 2.08 O4 . The present Mn-Zn ferrite has excellent magnetic properties because of the low porosity compared with ordinary ferrites.…”

Noncontact deep level photo-thermal spectroscopy: Technique and application to semi-insulating GaAs Wafers

“…In the midinfrared region, the fca is mainly caused by interaction with phonons in a semiconductor. 6,7 The dla absorption coefficient can be written as ␣ dla = dla n T cm −1 , where dla could also be considered a constant. 5 In a given wavelength, ␣ fca is proportional to the free carrier density, which can be expressed by ␣ fca = fca n͑t͒ cm −1 , where fca is the absorption cross section, which could be considered constant in a small temperature range ⌬T͑ϳ150 K͒.…”

Optical evaluation of the ionized EL2 fraction in proton (24 GeV) irradiated semi-insulating GaAs

“…8,9 A SI ͗100͘ oriented GaAs wafer ͑1 in. The adopted procedure consisted in measuring the optical absorption in the near infrared ͑IR͒ subgap region, which is mainly determined by the photoionization and the photoneutralization of EL2 0 and EL2 ϩ , respectively.…”