AlGaN/AlN/GaN HEMT结构2DEG的光致发光谱

Photoluminescence of 2DEG in AlGaN /AlN /GaN HEMT Structures

AlGaN/GaN HEMT结构材料主要用于研制微电子器件,对其发光性质的研究相对较少。通过对AlGaN/GaN HEMT结构材料的光致发光谱(PL)研究,观测到了AlGaN势垒层中Al组分为40%的AlGaN/AlN/GaN结构中二维电子气(2DEG)光致发光及其能级分裂现象。在4.5 K低温下,其2DEG发光峰在GaN带边峰能量以下30和40 meV处分裂成两个峰位,直至温度持续升高至40 K后消失。根据GaN价带顶部在单轴晶格场和自旋-轨道耦合共同作用下的能级分裂理论,因自旋-轨道耦合引起的2DEG发光峰两个分裂能级差约为10 meV,与实验测得的结果一致,因此实验观测到的2DEG发光峰的分裂现象是由于氮化镓价带能级的自旋-轨道耦合而形成的。

AlGaN /GaN structural materials are most used to fabricate microelectronic devices,whose optical characteristics are seldom studied. The two-dimensional electron gas（ 2DEG） photolumine-scence（ PL） emissions and the energy split in the undoped AlGaN /AlN /GaN HEMT structure with the Al composition of 40% were observed by the research of the photoluminescence（ PL）. An obvious additional 2DEG PL emission peak appeared at 30 meV and 40 meV below the band-edge emission of GaN at the low temperature of 4. 5 K and persisted up to 40 K. According to the uniaxial crystal field and spin-orbit coupling of GaN,it＇s known that the top of GaN valence band is split into three energy levels,and the energy level distance of PL emission peaks for the two valence band based on spin-orbit coupling is about 10 meV,which is consistent with the measured energy level distance of 2DEG emissions.Therefore the observed split in the experiment of the 2DEG emissions was caused by the spin-orbit coupling of GaN valence band energy level.