Long wavelength bulk absorption cutoffs in GaAs light-emitting diodes exhibiting vacuum and gamma-irradiation emission wavelength tunability

Absorption edge measurements indicate hardly any change in long wavelength detection cutoff of GaAs shallow-junction surface-emitting LED's as a result of pressure effects. This supports the concept that vacuum-induced significant emission wavelength tuning of these devices is a result of surface effects rather than changes in E
g
. Also, possible slight decrease of long wavelength cutoff in these devices via gamma irradiaition, while emission wavelength is shifted significantly to longer wavelengths, proves that γ-irradiation spectral tuning of them does not derive from bulk bandgap changes and supports the concept that emission wavelength increase in these shallow-junction devices is a result of effects of γ-irradiation on surface emission rather than on E
g
in the bulk.