Terahertz Absorption in Quantum Devices Based on MgxZn1-xO/ZnO Quantum Well Structures

The energy level structures of MgxZn1-xO/ZnO/MgxZn1-xO quantum wells (QWs) with various geometrical structures and material compositions are obtained. Terahertz (THz) intersubband absorption can be realized and tunable with x in the range of 0.01 similar to 0.04 and well width in the range of 5 similar to 13 nm. Electron scattering such as piezoelectric acoustic phonon (PAP), polar optical phonon (POP), interface roughness (IFR), and random alloy (RAS) scattering are included in the calculations to analyze the linewidth broadening. Increasing the Mg composition or decreasing the well width can obtain high-frequency THz intersubband absorption, in which case IFR is found to be the physical mechanism that makes the linewidth broaden. On the other hand, the influence difference of PAP scattering for the lower Mg composition, which may be caused by the different electro-mechanical coupling coefficients (EMCC), is obviously larger than that for the higher Mg composition, meaning that the accurate value of EMCC is much more important for the THz intersubband absorption in MgxZn1-xO/ZnO/MgxZn1-xO QWs with a smaller x. The findings are helpful in the design of THz detector devices.

Automated summary

The energy level structures of MgxZn1-xO/ZnO/MgxZn1-xO quantum wells with different geometrical structures and material compositions have been obtained. Tunable terahertz intersubband absorption can be achieved by adjusting the Mg composition and well width. The linewidth broadening is analyzed by including electron scattering mechanisms such as piezoelectric acoustic phonon, polar optical phonon, interface roughness, and random alloy scattering. The findings show that increasing the Mg composition or decreasing the well width can result in high-frequency terahertz intersubband absorption, with interface roughness playing a significant role in linewidth broadening.