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

利用分子束外延技术（MB）系统地研究在GaAs上生长的假晶InGaAs中应变梯度的存在。可以同时实现InA1As与InGaAs的晶格匹配和InA1As与A1GaAs的能量匹配。这允许一个测试结构，其中带隙不连续与应变界面无关。在第一个实验中，将使用MBE生长多个InGaAs/InA1As/GaAs单量子阱结构。量子阱在应变区内的位置将发生变化，使得量子阱充当测量应变的探针。在不同的应变层厚度下，将生长出几组样品。第二个实验与第一个实验重复，除了应变区域将保持在最小临界厚度以下。这允许在同一样本中生长所有测试结构，以便进行比较。生长后，将使用光致发光来检测应变引起的能带位移。如果伪晶InGaAs材料中应变梯度的假设得到证实，那么该项目将对伪晶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.