【摘要】 通过低温和强磁场下的磁输运测量研究了Al0 2 2 Ga0 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× 10 1 2 cm- 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率骤然下降 ,而且第二子带的电子迁移率远大于第一子带的电子迁移率 .用电子波函数分布和应变弛豫时的失配位错散射解释了上述现象 .同时进一步说明了界面粗糙散射和合金无序散射是决定AlxGa1 -xN GaN异质结构中 2DEG迁移率的主要散射机理更多还原

【Abstract】 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 7.3×10 12cm -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-xN/GaN heterostructures.更多还原