Characterization of gallium arsenide nitride and indium gallium arsenide nitride novel semiconductors

In this thesis, important properties of gallium arsenide nitride (GaAsN) and indium gallium arsenide nitride (InGaAsN) novel semiconductors are presented. Using several experimental techniques such as x-ray diffraction, photocurrent, photoluminescence, effusion, and secondary ion mass spectrometry, several characteristic properties are measured, analyzed, compared to theoretical predictions, and discussed.

Single layers of GaAsN were grown on GaAs (001) substrates. Single crystals with nitrogen concentrations of more than 5% were achieved. The incorporation of nitrogen in GaAs does not seem to be limited by an intrinsic solubihty limit, but by the growth conditions. The stability against phase separation was estimated from thermal treatment and was found to be highly satisfactory. Effusion experiments on GaAsN revealed that the increase in photoluminescence efficiency upon annealing is partly due to the removal of an important number of nitrogen atoms {^ 10^^ cm~^) incorporated on non-substitutional lattice sites. An accurate determination of the bandgap dependence on nitrogen concentration was made and compared with calculated dependencies. The bowing coefficient is found to be concentration dependent: it is close to 18 eV at low nitrogen concentrations while it is approximately 14 eV at nitrogen concentrations of 3.6%. Samples grown with active nitrogen provided by DMHy instead of plasma-cracked N2 show better luminescence efficiency, probably due to a higher background doping for DMHy-samples and/or the production of defects by high energy nitrogen ions for N2-samples. The formation of the bandgap of GaAsN is investigated for samples with low nitrogen concentrations. Low temperature photoluminescence yielded complex spectra of highly efficient radiative recombination centers similar to nitrogen pairs in GaP. These centers are tentatively attributed to exciton recombination bound to a pair of nitrogen related complexes.

Quantum wells of GaAsN were also grown on GaAs. The room temperature photoluminescence from two sets of multiple quantum wells (MQW) were analyzed. Using the valence band offset as a free parameter, the duplication of the experimental results with calculated optical transition energies yielded a type-II natural band alignment between GaAsN and GaAs. It was found the valence band of GaAsN shifts to lower values at a rate of approximately 50 meV per percent nitrogen. The accuracy and validity of these results is discussed.

Ordering in GaAsN samples was investigated with x-ray diffraction and polarized photoluminescence. However, no evidence of long range ordering could be found.

Single layers and multiple quantum wells made of InGaAsN were investigated. It was found that some nitrogen can be incorporated in InGaAs, but the nitrogen incorporation is apparently limited to very low nitrogen concentrations (^0.2%). This concentration is not enough to reach a emission wavelength of 1.3 /zm.