Electronic and Optical Properties of Mg x Zn1−x O and Be x Zn1−x O Quantum Wells

Abstract

As a preparatory step toward establishing reliable numerical design tools for ZnO-based optoelectronic devices, we have reassessed the available information on material parameters relevant for the simulation of light-emitting diodes (LEDs) with active regions including ZnO, MgZnO, and BeZnO layers. The impact of different approximations for the electronic structure and the interface polarization charge on the optical properties of bulk ZnO and ZnO/MgZnO quantum wells has been evaluated, and a consistent set of parameters has been used not only for systematic comparison of ZnO/MgZnO and ZnO/BeZnO single quantum well structures but also for the first simulation of a realistic ZnO/BeZnO multiple quantum well LED.

Band Structure and Effective Masses of Zn1-xMgxO

“…Some of the necessary physical parameters like the valence band effective masses are still unknown for finite concentrations. Thus, recent calculations have to resort to linear interpolation between the pure components, or even use the ZnO value for all concentrations [6]. The most important part of the ZnO band structure, which is the bottom of the conduction band and the top of the valence bands in the vicinity of the Γ-point, can be well described within the effective mass approximation.…”

ZnO-based deep-ultraviolet light-emitting devices

“…[64] Although Be x Zn 1−x O alloys each have a larger bandgap modulation range than the Mg x Zn 1−x O alloys without phase segregation, there are still problems caused by the difference in ionic radius between Be 2+ (0.27 Å) and Zn 2+ (0.60 Å), inducing a large lattice mismatch between BeO and ZnO. [65] The crystal quality of the resulting Be x Zn 1−x O films will be degraded with the increase of Be atomic content. To obtain high-quality ZnO-based films with bandgap modulation to DUV region, quaternary Be x Mg y Zn 1−x−y O alloys were proposed and investigated for applications in various optoelectronic devices.…”

Theoretical investigation of BeZnO-based UV LEDs

“…Table 2 provides the transport and recombination parameters employed to model carrier transport in the LED structure. Due to the paucity of experimental data available on BeZnO, the ZnO parameters of the low-field mobility models for electrons and holes [23][24][25], fitted from the results of Monte Carlo transport simulations [26], have been used for any alloy composition, while the Auger recombination coefficient has been derived by recent ab initio results on ZnO and MgZnO [27].…”