Investigation on the Deposition of an AlN-ZnO/ZnO/AlN-ZnO Double Heterojunction Structure Using Radio Frequency Magnetron Cosputtering Technology

Abstract

A symmetric AlN-ZnO/ZnO/AlN-ZnO double heterojunction structure was consecutively deposited onto silicon substrate using cosputtering technology and then annealed at 700 °C under vacuum ambient for 30 min. The crystalline quality of the ZnO film in the heterojunction structure was significantly improved as verified by X-ray diffraction (XRD) and photoluminescence (PL) measurements. Improvement on the crystalline structure was ascribed to the stress in the ZnO active film, which was effectively buffered by the underlayered AlN-ZnO layer. Native oxygen vacancies in the ZnO film also were effectively suppressed due to a little diffusion of the Al atoms from the cosputtered AlN-ZnO layer, and led to an increase in the carrier concentration. Such ZnO film deposited onto the homogeneous AlN-ZnO buffer layer emitted an intense near-band-edge emission, and the deep level emission was absent. The ultraviolet emission was further enhanced by covering an AlN-ZnO barrier laye, which was a consequence of the improvement on the carrier confinement. Accordingly, single ultraviolet emission with a quality ZnO crystalline structure, which is very promising for application in short-wavelength optoelectronic devices, was realized from the ZnO film sandwiched by the homogeneity of the cosputtered AlN-ZnO layers.

Dual-function of the ZnO nano-sheets as light absorber scaffold and electron transport material in perovskite solar cells

“…The shift of these peaks could be explained due to the difference in sizes of Zn and Al atoms. As the dopant, the smaller ions Al 3+ with radius of 0.053 nm substituted into Zn 2+ sites as the larger ion (0.072 nm) [32]. Therefore, the difference in the lattice parameters of the AZO and ZnO causes the shift in XRD peaks.…”

Enhancement of the near-band-edge electroluminescence from the active ZnO layer in the ZnO/GaN-based light emitting diodes using AlN-ZnO/ZnO/AlN-ZnO double heterojunction structure

“…As discussed in the previous work, the improvement in the ZnO film's crystallinity was demonstrated to be the diffusion of the Al atoms in the cosputtered AlN-ZnO film into the ZnO layer to suppress the formation of the native oxygen vacancies. These indiffused Al atoms to act as the Al Zn donor also led to the red-shift of the ultraviolet luminescence to about 388 nm, with a wider full width at half maximum (FWHM) [24]. Moreover, as listed in table 1, the activation of the Al Zn donor in the DH-ZnO structure resulted in a very high electron concentration in spite of the suppression of the V O donor.…”

“…In addition, Zheng et al also fabricated an AlN-ZnO/ZnO/AlN-ZnO DH structure using the rf magnetron cosputtering technology. The ZnO film sandwiched by the cosputtered AlN-ZnO film exhibited quality crystalline structure and showed enhancement of the NBE photoluminescence (PL) a consequence of the suppression of the native V O defects [24]. In this study, the AlN-ZnO/ZnO/AlN-ZnO DH structure was applied to consecutively deposit onto the p-GaN epilayer.…”