Composition And Hydrostatic Pressure Tuning For The Band Lineups Type In Quaternary Mixed Crystal In_1-xGa_xAs_yP_1-y/InGaAsP Quantum Wells

Quaternary mixed crystal semiconductor material has two independent components of variable,compared with the binary and ternary alloys,its lattice constant , band gap and other physical properties can be individually tuned by changing the composition. At present, the band gap, the lattice vibration properties, optical properties and quantum wells devices for quaternary material have been researched extensively, and some meaningful results have already been abtained. However, quantum-well structure entirely composed of the same quaternary material is seldom studied so far, and the band transition has not been reported.The controling of energy band structure, such as the band transition is an effective way for the energy band tailoring, device design and performance optimization, which has great significance in the energy band engineering. Currently, in addition to the composition modulation and doping modulation, the high pressure modulation has also become an important mean for studying a low-dimensional structure semiconductor. Here, we will control the band structure of quantum-well system that is composed of InGaAsP by changing the composition and the hydrostatic pressure.In this paper, the band structure of quaternary mixed crystal semiconductor quantum wells is investigated by using the model solid theory by considering the strain effect induced by the lattice mismatch as well as the composition and hydrostatic pressure modulation effects on the band lineups. The strain in the quantum-well is also used as the probing of the possibility of transition of the band lineups type and transformation of strain type under the concentration and pressure modulation. Furthermore, we will also discuss the band lineups for electrons and holes tuned by changing concentration when the quantum well is with multilayers. For the quantum-well structure entirely composed of the InGaAsP quaternary mixed crystal material, the band profiles of electron and hole in In_1-xGa_xAs_yP_1-y quantum wells are investgated by using model solid theory under the condition that lattice parameter in the barrier material matches with the InP substrate. The conduction-band offset and valence-band offset and the lattice mismatch (strain) and band gap variations over the entire range of composition (x,y) in the well material are calculated . It is shown that the band lineup of quantumn wells emerges the transition from type-I to type-II when the barrier material composition is fixed, whereas the well material composition is changing. Strain within the quantum wells also changes from the compressive strain to the tensile strain correspondly. It is possible to realize parabolic quantum wells by changing material composition for multi-storey SQW.The hydrostatic pressure is introduced to discuss the pressure effect of the band lineups for electron and hole in the quantum wells. Stress influence on the lattice constant and the elastic constant is considered simultaneously. Numerical the conduction-band offset and valence-band offset and the lattice mismatch as functions of hydrostatic pressure and composition are calculated. Only the hydrostatic strain is considered in the barrier layer, while the hydrostatic strain and internal biaxial strain are involved in the well layer simultaneously. It is found that pressure tuning can also lead to transition of the band lineups type no matter the well material composition is fixed or not. Moreover, pressure modulation can cause the strain transition, too. By further calculating, we also discover that for the well material with fixed composition, the smaller Arsenic component y is in the barrier layer, the greater the transition pressure is. The smaller Gallium component x is in the barrier layer, the smaller the transition pressure is.