Existence of Strain Gradients in Pseudomorphic InzGa (1-z) As/GaAs Material Grown Using Molecular Beam Epitaxy

为了系统地研究分子束外延(MB)生长在GaAs基上的假晶InGaAs中应变梯度的存在。可以同时实现InAlAs与InGaAs的晶格匹配和InAlAs与AlGaAs的能量匹配。这允许测试结构，其中带隙不连续性与应变界面无关。在第一个实验中，我们将用分子束外延生长几种InGaAs/InAlAs/GaAs单量子阱结构。量子井在应变区中的位置将会改变，以便量子井充当测量应变的探测器。几组样品将以不同厚度的应变层生长。第二个实验重复了第一个实验，只是应变区将保持在最小临界厚度以下。这允许在相同的样品中生长所有测试结构以进行比较。生长后，将通过光致发光来检测应变诱导的频移来测量应变。如果假象InGaAs材料中的应变梯度假设被证实，那么该项目将对假象MODFET(HEMT)器件的设计和制造产生重大影响。

To systematically investigate the existence of strain gradients in pseudomorphic InGaAs grown on GaAs using molecular beam epitaxy (MB). It is possible to simultaneously lattice-match InA1As with InGaAs and energy-match InA1As with A1GaAs. This permits a test structure where the bandgap discontinuity is independent of the strained interface. In the first experiment, several InGaAs/InA1As/GaAs single quantum well structures will be grown using MBE. The location of the quantum well within the strained region will be varied such that the quantum well serves as a probe to measure the strain. Several sets of samples will be grown with different thicknesses of the strained layer. The second experiment duplicates the first except the strained region will be kept substantially below the minimum critical thickness. This permits all of the test structures to be grown in the same sample for comparison purposes. After growth, the strain will be measured by using photoluminescence to detect strain-induced band shifts. If the hypothesis of strain gradients in pseudomorphic InGaAs material is confirmed, then this project will have significant impact on the design and fabrication of pseudomorphic MODFET (HEMT) devices.