Recombination processes with and without momentum conservation in degenerate InN

Evgenia Valcheva 3S. Alexandrova 1S. Dimitrov 3H. Lu 2William J. Schaff 2

1. Institute of Solid State Physics, Bulgarian Academy of Sciences (ISSP-BAS), 72, Tzarigradsko Chaussee blvd., Sofia 1784, Bulgaria
2. Cornell University, Electrical and Computer Engineering, Ithaca, NY 14853-540, United States
3. Sofia University, Dept. of Solid State Physics and Microelectronics, 5 J. Bourchier blvd., Sofia 1164, Bulgaria

Abstract

The evaluation of InN fundamental properties and parameters like band gap, effective mass values, phonon modes, etc., of both poly- and monocrystalline InN layers is a subject of permanently growing number of reports. Photoluminescence experiments are widely used to investigate the nature of the recombination processes. Applied to high concentration material the experiment is usually used for the determination of the effective optical band-gap assuming band filling and renormalization effects.
We report on a theoretical approach in which two cases of recombination in optically excited high concentration n-InN are considered: an electron occupying a conduction state can only decay to a valence state with the same wave vector, and the other, in which the probability is essentially independent of the wave vectors of the two states (no momentum conservation). The latter is applicable when the donors have random distribution in the real space. For high impurity concentrations the periodicity of the lattice is perturbed and the momentum conservation is partly lifted so that all available carriers can contribute to the total radiative recombination. The calculations are used to fit emission spectra of unintentionally doped (~1×1018 -1×1019cm–3) InN layers studied in the temperature range 10-300K with excitation wavelength of 488 nm and recorded with PbS detector. The spectra peak at around 0.7eV and can be well fitted disregarding the momentum conservation law.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium A, by Evgenia Valcheva
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-30 13:27
Revised:   2009-06-07 00:44
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