Effect of uniaxial stress on gallium, beryllium, and copper-doped germanium hole population inversion lasers [electronic resource].
- Washington, D.C. : United States. Dept. of Energy. Office of Energy Research, 1998. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- 69 pages : digital, PDF file
- Additional Creators:
- United States. Department of Energy. Office of Energy Research and United States. Department of Energy. Office of Scientific and Technical Information
- The effects of stress on germanium lasers doped with single, double, and triple acceptors have been investigated. The results can be explained quantitatively with theoretical calculations and can be attributed to specific changes in the energy levels of acceptors in germanium under stress. In contrast to previous measurements, gallium-doped Ge crystals show a decrease in lasing upon uniaxial stress. The decrease seen here is attributed to the decrease in heavy hole effective mass upon application of uniaxial stress, which results in a decreased population inversion. The discrepancy between this work and previous studies can be explained with the low compensation level of the material used here. Because the amount of ionized impurity scattering in low-compensated germanium lasers is small to begin with, the reduction in scattering with uniaxial stress does not play a significant role in changing the laser operation. Beryllium-doped germanium lasers operate based on a different mechanism of population inversion. In this material it is proposed that holes can transfer between bands by giving their energy to a neutral beryllium atom, raising the hole from the ground to a bound excited state. The free hole will then return to zero energy with some probability of entering the other band. The minimum and maximum E/B ratios for lasing change with uniaxial stress because of the change in effective mass and bound excited state energy. These limits have been calculated for the case of 300 bar  stress, and match very well with the observed data. This adds further credence to the proposed mechanism for population inversion in this material. In contrast to Be and Ga-doped lasers, copper-doped lasers under uniaxial stress show an increase in the range of E and B where lasing is seen. To understand this change the theoretical limits for population inversion based on both the optical phonon mechanism and the neutral acceptor mechanism have been calculated. The data are described by population inversion via optical phonons at zero pressure. However, both mechanisms most likely occur when the slightly higher, non-uniform pressures of 300 bar are applied, leading to an increase in population inversion and lasing. Upon further increasing the pressure to 600 bar, the limits for population inversion decrease and a decrease in the lasing is seen.
- Dissertation Note:
- Thesis submitted to Univ. of California, Berkeley, CA (US); TH: Thesis (M.S.); PBD: May 1998
- Published through SciTech Connect., 05/01/1998., "lbnl--41854", "DE98056112", Chamberlin, D.R., and Lawrence Berkeley National Lab., Materials Sciences Div., Berkeley, CA (United States)
- Funding Information:
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