Shimin Huang

Temperature-dependent photoluminescence of ZnO films codoped with tellurium and nitrogen

The photoluminescence spectra as well as their temperature dependence of the tellurium and nitrogen (Te-N) codoped ZnO films have been investigated in detail. Explicit evidences of the emissions related to two acceptors [A1: the NO-Zn-Te subunits and A2: the conventional N ions substituting on oxygen sites (NO)] have been found. The acceptor activation energy level of the A1 (∼118–124 meV) is much shallower than that of the A2 (∼224–225 meV) indicating that the A1 should be mainly responsible for the room-temperature p-type nature of the codoped samples. Meanwhile, the acceptor activation energy level of A1 shows a slight decrease (∼6 meV) as the Te atomic concentration increases in the codoped samples implying that the actual form of the A1 may be a mixture of the NO-Zn-nTe (n = 1, 2, 3, 4). More incorporation of the Te ions into N-doped ZnO films not only makes the acceptor energy level shallower but also improves the crystalline quality and results in the efficiently suppressed native donorlike defects...

Influence of oxygen precursors and annealing on Fe3O4 films grown on GaN templates by metal organic chemical vapor deposition

O2 and N2O, popular oxygen precursors for oxide films growth, have been employed to grow Fe3O4 films on GaN templates via metal organic chemical vapor deposition (MOCVD). A (111)-oriented Fe3O4 film was preferably deposited when N2O was used as O precursor, while a Fe2O3 film was grown with O2 as O precursor. A high-temperature annealing has caused a phase transition from α-Fe2O3 to Fe3O4 for O2 case, but no obvious change occurred on the Fe3O4 film for N2O case. Thinner Fe3O4 layer was then grown on a GaN template with N2O as O precursor to form ferromagnetic material (FM)/nonmagnetic material (NM) heterostructure, which is critical for the realization of spin injection in GaN based wide band gap semiconductors. The Ga diffusion from the GaN template to the Fe3O4 layer has been controlled at a rather low level possibly due to the employed low-temperature growth, leading to a high-quality FM/NM heterostructure. An obvious enhancement on the Ga diffusion has been observed upon subsequent annealing for the ...

Mutually beneficial doping of tellurium and nitrogen in ZnO films grown by metal-organic chemical vapor deposition

The advantages of tellurium-nitrogen (Te-N) codoping are investigated in ZnO films grown by metal-organic chemical vapor deposition. Te incorporation gives aid in enhancing the N solubility by lowering its formation energy while N addition helps to stabilize the substituted Te on O sites with the phase-segregated ZnTe crystallites suppressed by forming the N-Zn-Te structures in the N-doped ZnTexO1−x. Carbon related impurities, commonly existing in N-doped ZnO and acting as compensating centers for holes, are fully eliminated by the Te-N codoping. The codoping technique also lowers the energy level of the NO acceptors and leads to realizing N-doped ZnTexO1−x films with holes as major carriers.

Thermal pretreatment of sapphire substrates prior to ZnO buffer layer growth

This research was supported by the State Key Program for Basic Research of China under Grant No. 2011CB302003, National Natural Science Foundation of China (Nos. 61025020, 60990312, and 61274058), Basic Research Program of Jiangsu Province (BK2011437), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Temperature-dependent exciton-related transition energies mediated by carrier concentrations in unintentionally Al-doped ZnO films

The authors reported on a carrier-concentration mediation of exciton-related radiative transition energies in Al-doped ZnO films utilizing temperature-dependent (TD) photoluminescence and TD Hall-effect characterizations. The transition energies of free and donor bound excitons consistently change with the measured TD carrier concentrations. Such a carrier-concentration mediation effect can be well described from the view of heavy-doping-induced free-carrier screening and band gap renormalization effects. This study gives an important development to the currently known optical properties of ZnO materials.

Thermal treatment induced change of diluted oxygen doped ZnTe films grown by metal-organic chemical vapor deposition

In this paper, the authors report the growth of diluted oxygen doped ZnTe films (ZnTe:O) by metal-organic chemical vapor deposition (MOCVD). The effect of a post thermal annealing on the properties of the highly mismatched films has been investigated. It is found that the in-situ doping leads to an effective incorporation of oxygen into ZnTe films with different occupation configurations, either on Zn or on Te site. The subsequent annealing process in a vacuum ambient leads to an enhancement of the oxygen incorporation into the ZnTe:O films due to the diffusion of the residual oxygen, while the annealing with the same as-grown sample covered on top of the surface (denoted as “face-to-face” annealing in the text) is beneficial to the improvement of the film quality with manifest intermediate band emission at around 1.9 eV as revealed by the low-temperature photoluminescence. This study indicates that the mass-productive MOCVD technique may be suitable for the growth of highly mismatched ZnTe:O films for th...