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Uniaxial stress effect on photoluminescence from GaNAs/GaAs quantum wells and GaN/AlGaN heterostructures

Authors Lee, Chi Yung
Issue Date 2000
Summary The theory of semiconductor (quantum well and short period superlattice) under different directions of uniaxial stress was studied. For the stress effect on the valence subbands, by using the 4x4 Luttinger-Kohn and strain Hamiltonian in the spin of J = 3/2 basis, the heavy and light hole valence subbands might cross over under stress X//[00l] (the growth direction) at k[subccript //] = 0. For the theory of type II indirect short period superlattice under uniaxial stress, the response of conduction band minimum (CBM), i.e. X state, would be different under different stress directions. The experimental set up for applying stress along different directions was designed. In order to apply uniaxial stress on sample, a pressure system was used and the pressure was recorded by a digital pressure gauge. If the applied stress is X//[00l], i.e. along the growth direction of the epi-layers, the longitudinal sample tube was used and the laser light should be introduced at the bottom of the sample tube. Also, the transverse sample tube should be used if the applied stress direction was along other directions, such as [100], [1l0] or [111]. In the experimental parts, two quantum well samples of GaAs(1-x)Nx with x= 1.5% and 2.63% were studied under uniaxial stress X//[00l] at 77k. Both of the results showed a turning at certain value of stress (1.75kbar and 1.5kbar respectively). The type II (indirect) short period superlattice semiconductor of (GaAs)4/(AlAs)4 was studied by applying uniaxial stress along [00l], [1l0] and [100]. By applying stress X//[00l], the peak energy showed a red shift of -4.3lmeV/kbar. Besides, when the applied stress is X//[1l0] or [100], the peak energy showed a little bit blue shift of 0.36meV/kbar and 0.38meV/kbar, respectively. When comparing the experimental result with the theoretical value, it was found that the shift was consistent with the theory and more or less the same as the previously reported value. Finally, a sample of AlGaN/GaN heterostructure was studied under uniaxial stress X//[00l]. All of the six peaks showed blue shift when the stress increased. The energy shifts of peak 4 and 5 were 1.4meV/kbar and 2.12meV/kbar, respectively. Since peak 1 did not show a linear shift, it was suggested that this peak should be from a deep level.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2000
Language English
Format Thesis
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