Control of interface abruptness of polar MgZnO/ZnO quantum wells grown by pulsed laser deposition

Abstract

A strong quantum confined Stark effect (QCSE) was observed in wedge shaped MgZnO/ZnO quantum wells (QWs) grown by pulsed laser deposition. A reduced laser fluence of 1.8 J/cm2 was used. Reference samples grown at higher standard fluence 2.4 J/cm2 showed only a negligible QCSE. Using off-axis deposition without substrate rotation, a constant composition of the barriers was maintained while varying the well width in a wedge shaped QW. A redshift of the QW luminescence with increasing QW thickness up to 230 meV below the ZnO emission was found, accompanied by an increase in the exciton lifetime from 0.3 ns up to 4.2 μs.

Thermal stability of ZnO/ZnCdO/ZnO double heterostructures grown by pulsed laser deposition

“…Due to our growth process in which pure CdO is deposited but Zn 1Àx Cd x O with a small Cd-content is formed, we assume an intermixing during growth. As the energy of fast ionic species in the PLD plasma can be as high as some hundreds of electronvolts this intermixing is reasonable [17,18]. Hence, already for the as-grown structure a Gaussian like Cd-profile in growth direction occurs:…”

“…Although we deposited pure CdO, Zn 1Àx Cd x O with a small Cd-content is formed, as result of intermixing already during the growth. This can be easily understood by taking into account the high energy of fast ionic species in the PLD plasma that can be as high as some hundreds of electronvolts [17,18].…”

Directional and magnetic field enhanced emission of Cu-doped ZnO nanowires/<italic>p</italic>-GaN heterojunction light-emitting diodes

“…Previously, it has been shown that it is possible to tune the bandgap of ZnO films by addition of dopants. 13,[26][27][28][29] For instance, the emission wavelength could be tuned and redshifted toward the violet-blue region by almost 40 nm by doping with Cu. 13 The addition of dopant can permit bandgap control in semiconductors and creates barrier layers which will facilitate radiative recombination by carrier confinement.…”

“…13 The addition of dopant can permit bandgap control in semiconductors and creates barrier layers which will facilitate radiative recombination by carrier confinement. 28,29 The top layer was spaced by a thin polymer insulator in order to avoid the direct contact between the GaN layer and the collapse of the nanowires. Our system permitted to take a top contact on Cu:ZnO nanowires with an ITO layer and to keep air, a low refractive index medium, between the Cu:ZnO nanowires.…”

Exciton confinement in homo- and heteroepitaxial ZnO/Zn1 − xMgxO quantum wells with x &lt; 0.1

“…3 Several groups have investigated heteroepitaxial growth of ZnO/(ZnMg)O single heterostructures, [4][5][6] single quantum wells (SQWs), [7][8][9][10][11][12][13][14][15] double quantum wells, 16 and multiple quantum wells [17][18][19] on various substrates such as c-plane, a-plane, and r-plane sapphire, c-plane GaN/sapphire templates, Si(111), and ScAlMgO 4 . However, only very few results of homoepitaxial growth of polar ZnO/(ZnMg)O SQWs have been reported, 20 although this growth technique can lead to improved structural, optical, and electrical properties of the resulting ZnO films.…”