AlxGa1-x N/GaN调制掺杂异质结构的子带性质研究

通过低温和强磁场下的磁输运测量研究了Al_0.22Ga_0.78N/GaN调制掺杂异质结构中2DEG的子带占据性质和子带输运性质.在该异质结构的磁阻振荡中观察到了双子带占据现象，并发现2DEG的总浓度随第二子带浓度的变化呈线性关系.得到了该异质结构中第二子带被2DEG占据的阈值电子浓度为7.3×10¹²cm^-2.采用迁移率谱技术得到了不同样品的分别对应于第一和第二子带的输运迁移率.发现当样品产生应变弛豫时第一子带的电子迁移 关键词： AlGaN/GaN异质结 二维电子气 子带占据 输运迁移率

Study on the subband properties of AlxGa1-x N/GaN modulation-doped heterostructures

The subbands occupation and subband transport properties in modulation-doped Al_0.22Ga_0.78N/GaN heterostructures are studied by means of magnetotransport measurements at low temperatures and high magnetic fields. The occupation of two subbands is observed from the Shubnikov-de Haas oscillations. It is found that the total density of the two-dimensional electron gas (2DEG) as a function of the electron sheet density in the second subband is linear. The threshold of the 2DEG density that the second subband begins to be occupied is 7.3×10¹²cm^-2. The transport mobility of the 2DEG in the two subbands is obtained by using the mobility spectrum technique. It is found that the transport mobility in the first subband decreases significantly when the relaxation of the Al_0.22Ga_0.78N barrier occurs. The electron mobility in the second subband is much larger than that in the first one. The results indicate that the interface roughness scattering and the alloy disorder are the main mechanisms in determining the 2DEG mobility in Al_xGa_1-x N/GaN heterostructures.