Thermal stability of CdZnO∕ZnO multi-quantum-wells

Abstract

The thermal stability of CdZnO / ZnO multi-quantum-well ͑MQW͒ structures was studied using rapid thermal annealing in nitrogen from 300 to 750°C. Photoluminescence ͑PL͒ emission from the MQWs was studied while varying the annealing temperature and time. For 15 min annealings, the PL center wavelength showed a 7 nm reduction for temperatures up to 650°C. Above 650°C, the wavelength changed rapidly, with a 50 nm reduction at 750°C. Annealing at 700°C for up to 20 min produced a systematic reduction in PL wavelength up to 39 nm. The data suggest that CdZnO / ZnO MQWs are relatively stable for nitrogen annealing below 650°C for times up to 15 min.

Optical properties of sputtered hexagonal CdZnO films with band gap energies from 1.8 to 3.3eV

“…Among the materials to narrow the band gap of ZnO, the ternary semiconductor Cd x Zn 1−x O, alloying ZnO with CdO, is most promising [4,5]. The main reasons are as follows: (1) Cd and Zn ions have similar ionic radii of ∼0.74 and 0.60Å, respectively; (2) CdO has a direct band gap of ∼2.3 eV at room temperature, ∼1.0 eV narrower than that of ZnO [6,7]. In recent years, a variety of methods have been employed to deposit Cd x Zn 1−x O films, such as pulsed laser deposition [4,8], molecular beam epitaxy [9][10][11], metalorganic vapor-phase epitaxy [12,13], and magnetron sputtering [14].…”

“…Moreover, the thermodynamic solubility of CdO in CdO-ZnO alloying system is quite small i.e. ∼2 mol% in thermal equilibrium condition [7,15,16]. Therefore, it is very difficult to grow single-phase hexagonal Cd x Zn 1−x O films with high Cd contents.…”

Optical properties and microstructure of 2.02-3.30 eV ZnCdO nanowires: Effect of thermal annealing

“…These changes need to be accounted for and understood, especially for the case of ZnCdO, since Cd has a strong tendency to diffuse. 12 In the present study, we have used a combination of photoluminescence (PL), high resolution x-ray diffraction (HRXRD), high resolution transmission electron microscopy (HRTEM), and micro energy dispersive x-ray spectroscopy (micro-EDX) to quantitatively analyze the incorporation of Cd in ZnCdO nanowires with wurtzite structure, as well as the impact that post-growth thermal annealing has on their microstructure and radiative efficiency.…”

Temperature-dependent photoluminescence of CdZnO thin films grown by molecular-beam epitaxy

“…However, due to the difficulties in alloying large amounts of Cd into ZnO [1], CdZnO materials with bandgap smaller than 3.0 eV have not been achieved for a long time until recently [4][5][6][7]. Consequently, comprehensive studies on large-Cd-concentration CdZnO (E g o 3.0 eV) materials were rarely reported compared to the studies of small-Cd-concentration CdZnO materials [8][9][10][11][12][13][14][15][16]. In particular, the temperature-dependent photoluminescence (PL) studies of CdZnO materials with bandgap reaching the visible region were rarely reported, although these studies are critically important to extract material parameters for future device applications such as lightemitting devices with CdZnO as active layers.…”