Buffer Layer Influence On Optical Absorption Of Electron Intersubband Transition In Binary Energy Level Systems Of Quantum Wells

Adopting a finite difference method the Schrodinger equation is solved to obtain the eigenenergies and eigenwave functions of electrons in ZnO/MgxZn1-xO quantum wells(QWs)by taking account of the influence on the heterojunction potentials from a lot of factors such as mixed crystal component variation and the built-in electric fields induced by spontaneous and piezoelectric polarizations.The influences from buffer layer thickness,the widths of well and right barrier,and ternary mixed crystal(TMC)on the left barrier of critical width in this kind of binary energy level QW systems are investigated.Furthermore,the optical absorption coefficients of electronic intersubband transitions and the influences from the widths of each layer material and TMC effect are discussed using Fermi's golden rule.Firstly,the development of related researches and applications of QWs are briefly introduced,and the research history and progress about transition optical absorption of electrons are mainly introduced.The research status of optical absorption of electron intersubband transitions in ZnO/MgxZn1-xO QWs is described in detail.It is pointed out that the buffer layer of ZnO importantly influences the optical absorption of electron intersubband transitions in ZnO/MgxZn1-xO QWs.Further,the influence of size effect on binary energy level systems of ZnO/MgxZn1-xO QW with a buffer layer of ZnO is discussed in detail.Based on this,the effects of size and TMC on the intersubband optical absorption in the QWs are investigated.Our results indicate that there is a definite confinement from the buffer layer of ZnO on the left barrier,or a minimum value of left barrier width is needed.It is named as the critical width.The critical width of left barrier decreases with increase of the well width and Mg component,and increases with the increase of the right barrier width and buffer layer thickness.Besides,the effects of buffer layer thickness,the widths of left barrier,well and right barrier as well as TMC also impact on optical absorption induced by the electronic intersubband transitions.There is a blue-shift of absorption peak as increasing Mg component,the widths of right barrier and left barrier.Whereas,increasing well width will make the absorption peak red-shift.The above conclusions are expected to give theoretical guidance for improving the opto-electronic properties of materials and devices made of these heterostructures.