InN金属-绝缘体-半导体器件的制作及低温输运测量

Indium nitride (InN), as a promising semiconductor for infrared and electronic application, has always been a popular research topic in worldwide. However, on InN surface, there is a unique surface state-surface electron accumulation layer(SEAL), which hampers the efforts in realizing p-type InN, Schottky contact to InN and related InN devices. .We devote ourselves to the fabrication of InN Metal-Insulator-Semiconductor(MIS) structures and the low-temperature transport measurements of this MIS structures. We are mostly interested in the transport properties of InN SEAL, which may find a way to control the transport behavior of InN SEAL. So that the understanding of P-type InN can be improved. Compared with the widely used electrolyte-based Schottky contact(which is only stable near room temperature and not convenient due to its big size,liquid form and active chemical property) to InN , the MIS structure is much stable against the extreme experimental condition, like the routine low temperature(77K,4.2 K or below) required by electrical transport experiments. .Using this InN MIS structure, we will try to modulate the electron concentration in SEAL. Then combining the method of low-temperature and temperature-varying measurements, we may find some important rules governing the evolution of the electronic structures of InN surface states. At the same time, some non-trivial topics, like the transition from surface state transport to bulk state transport, the multiple subband transport can be observed. Some basic parameter of InN SEAL, e.g. the activation energy of electrons in SEAL, can also be measured independently and precisely. Then the effectiveness of previously widely used "multi-layer" method for SEAL can be checked and improved..This work mainly includes three parts: material growth, device fabrication and low-temperature measurements. Both the basic physics and device applications may benefit from our efforts.

本研究将致力于制作氮化铟(InN)金属-绝缘体-半导体（MIS）器件结构，并对其做低温电学输运的测量，研究InN 表面电子聚积层的输运特性，以期能够找到控制InN 表面态输运的方法。我们所要采用的MIS结构能够很方便的在各种极端条件下实现肖特基接触。这解决了InN研究界广泛使用的电解液接触只能在室温附近稳定使用的不便。利用MIS结构，我们将尝试控制InN 表面态中的电子浓度，再利用低温和变温的手段，找到InN 表面态中的电子结构的变化的规律。 同时，一些有趣的问题，比如InN中由表面态输运到体材料输运的转变，InN 表面层中的多子带输运，也有望被观察到。我们的工作还能验证一些研究InN 表面层的间接方法（比如多层模型）的有效性。本研究包括了InN材料生长，器件制作和低温电学测量几部分，将加深人们对InN的器件应用和物理特性的了解。

我们制作了InN金属-绝缘体-半导体器件，输运测量表明InN的表面电子聚积层有效屏蔽了外加栅极电场对沟道电流的影响，表明该表面层可能具有非常低的迁移率和极高的电子浓度。另外，我们在2.5K-280K的温度范围内对栅极电流(Ig)与栅极电压(Vg)关系进行了研究， 结果表明: (1) 栅极漏电主要是通过空间电荷限制输运（即Ig|Vg|n, n2）的机制进行; (2)在≤200K的温度下，绝缘体中电子陷阱(trap)不参与漏电，即n≈2；(3)在高温下，陷阱开始参与漏电，导致空间电荷倾向于均匀地分布在绝缘层中，导致指数n增加。我们进一步开展了InN光电导的实验工作。利用发光二极管（而不是激光），我们研究了InN薄膜在2.5K-280K温度范围以及一个相对干净的辐射环境（没有外界300K背景黑体辐射）中的光电导行为。虽然我们观察到了InN的负的光电导，但是该光电导并不具有之前别人所报道的“持续”的时间特征，而是一个很快的响应行为。实验表明，光的加热作用可以导致InN产生人为的负持续光电导现象。进一步的，我们发现强光和高温可以触发光电导过程中本征的非线性行为，导致光电导的幅度成为一个温度/（光强）的非单调函数。这个可能是之前关于InN光电导的报道互相不自洽的原因。