Photoconductive Properties of GaAs1-xNx Double Heterostructures as a Function of Excitation Wavelength

The ternary semiconductor GaAs1-xNx with 0 < x < 0.3 can be grown epitaxially on GaAs and has a very large bowing coefficient. The alloy bandgap can be reduced to about 1.0 eV with about a 3% nitrogen addition. In this work, we measured the internal spectral response and recombination lifetime of a number of alloys using the ultra-high frequency photoconductive decay (UHFPCD) method. The datashows that the photoconductive excitation spectra of the GaAs0.97N0.03 alloy shows a gradual increase in response through the absorption edge near Eg. This contrasts with most direct bandgap semiconductors that show a steep onset of photoresponse at Eg. The recombination lifetimes frequently are much longer than expected from radiative recombination and often exceeded 1.0 ms. The data wereanalyzed in terms of a band model that includes large potential fluctuations in the conduction band due to the random distribution of nitrogen atoms in the alloy.