Strong excitonic transition of Zn1−xMgxO alloy

Abstract

A strong excitonic optical transition in a Zn1−xMgxO alloy grown by radical source molecular beam epitaxy was observed using both optical reflectivity measurements and photoluminescence (PL) measurements. Clear and strong reflectance peaks at room temperature (RT) were observed from 3.42eV (x=0.05)to4.62eV (x=0.61) from ZnMgO layers at RT. Distinct clear PL spectra at RT were also observed for energies up to 4.06eV (x=0.44). The peak intensity of the reflected signal increased for x values up to x∼0.2 simultaneously with an increase in PL intensity; however, a Stokes shift between the reflectance peak and the PL peak was not observed for x values below 0.2. These facts suggest that the oscillator strength of ZnMgO is enhanced by alloying, and the underlying mechanism is discussed. Furthermore, we demonstrate that the strong reflectance properties even at RT provide an easy method to determine the Mg composition of a thin ZnMgO layer in a ZnMgO∕ZnO heterostructure.

Solar-blind 4.55eV band gap Mg0.55Zn0.45O components fabricated using quasi-homo buffers

“…4 in combination with reflectance spectrometry by using differential absorption coefficient versus photon energy, in which Urbach tail and Elliott's formula were employed to describe the innerbandgap and inter-band transition [16][17][18]. Additionally, excitonic transition peaks [13] can be observed in the high-energy side of the reflection spectra of both samples A and B with transition energy of 4.55 and 3.92 eV, respectively. Finally, the band gap in our Mg 0.55 Zn 0.45 O was found to be as high as 4.55 eV well entering into the solar-blind UV region.…”

“…Anyhow, addressing the issues several types of buffer layers with hexagonal surface structures, specifically RS-MgO (111) and W-ZnO (0 0 0 1), were used for growing MgZnO films epitaxially on c-sapphire substrate [10,11]. For example, singlephase W-MgZnO with a band gap of 3.99 eV was prepared by pulsed laser deposition [12], and a Mg 0.44 Zn 0.56 O film with a band gap of 4.25 eV was demonstrated using ZnO buffer layer by molecular beam epitaxy (MBE) [13]. Note, the synthesis of MgZnO with high Mg fractions used to suffer from severe reproducibility problems as often honestly emphasized by the authors [14].…”

Tuning ferromagnetism in zinc oxide nanoparticles by chromium doping

“…m h is the total mass of the e-h pair, 'R' is the radius of the nanoparticle, 'E g ' is the bulk band gap energy and 'E exc ' is exciton binding energy and 'n' is the quantum number. Tampo et al (2007) have reported that the band gap has cubic relation with the oscillator strength and the oscillator strength increases with increase in Mg doping in ZnO. The overlapping and splitting of valence band (VB) and conduction band (CB) states are mainly caused by the Cr impurity band near the Fermi level that has been fused into CB states (Bakhtiar et al 2014).…”

Properties of gallium- and aluminum-doped bulk ZnO obtained from single-crystals grown by liquid phase epitaxy

“…Most of the recent investigations on doped ZnO have been carried out using thin film materials [9][10][11] because thin film deposition techniques are directly related to the fabrication processes for optoelectronic devices [1][2][3]12,13]; however, such studies use thin film materials, which pose some limitations and difficulties. For example, properties of ZnO thin films are strongly affected by the physical and chemical states at the film/substrate interface [14]; moreover, preparation of thin films at relatively low temperature results in non-equilibrium structures [8,15,16].…”