The spin-splitting energy in wurtzite structure semiconductors had been investigated by linear combination of atomic orbital method (LCAO), atomic bond orbital method and two-band k¡Ep method. In order to explain the large zero field spin splitting in wurtzite GaN, a different mechanism (£GC1¡V£GC3 coupling) was proposed, which originated from the intrinsic wurtzite effects (band folding and wurtzite bulk inversion asymmetry). The band-folding effect generates two conduction bands (£GC1 and £GC3), in which p-wave probability has tremendous change when kz approaches the anticrossing zone. The spin-splitting energy induced by the£GC1¡V£GC3 coupling and wurtzite bulk inversion asymmetry is much larger than theory calculation of Kane model. When we apply the coupling to GaN/AlN quantum wells, we find that the spin-splitting energy is sensitively controllable by an electric field.
It is also found that ideal wurtzite bulk inversion asymmetry yields not only a spin-degenerate line (along the kz axis; time reversal axis) but also a minimum-spin-splitting surface, which can be regarded as a spin-degenerate surface in the form of bkz2- k//2=0 (b≈4) near the £F point. This phenomenon is referred to as the Dresselhaus effect (defined as the cubic-in-k term) in bulk wurtzite materials because it generates a term £^wz(bkz2- k//2)(£mxky-£mykx)=0 in the two-band k¡Ep Hamiltonian. And it is also demonstrated that in the k.p scheme, the spin splitting vanishes to cubic order in k. Consequently, the D¡¦yakonov-Perel¡¦ (DP) spin relaxation mechanism can be effectively suppressed for all spin components in [001] wurtzite quantum wells (QWs) at a resonance condition through device design with appropriate strain, gate voltage or optical illumination.
In conclusion: (1) the spin-splitting energy is enhance by wurtzite bulk inversion asymmetry; (2) the spin-splitting energy in wurtzite quantum well is sensitively controllable by electric field; (3) there exist a spin degenerate surface for wurtzite materials in k¡Ep scheme. Therefore, wurtzite QWs (e.g., InGaN/AlGaN and InN/AlInN) are potential candidates for spintronic devices such as the resonant spin lifetime transistor.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0208110-132907 |
| Date | 08 February 2010 |
| Creators | Wang, Wan-Tsang |
| Contributors | Meng-En Lee, Feng-Chuan Chuang, De-Hone Lin, Ikai Lo, Chun-Nan Chen, Jih-Chen Chiang, Jiann-Shing Shyu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0208110-132907 |
| Rights | campus_withheld, Copyright information available at source archive |
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