In-rich Al_xIn_1−xN grown by RF-sputtering on sapphire: from closely-packed columnar to high-surface quality compact layers

Abstract

The structural, morphological, electrical and optical properties of In-rich AlxIn1−xN (0 < x < 0.39) layers grown by reactive radio-frequency (RF) sputtering on sapphire are investigated as a function of the deposition parameters. The RF power applied to the aluminum target (0 W–150 W) and substrate temperature (300 °C–550 °C) are varied. X-ray diffraction measurements reveal that all samples have a wurtzite crystallographic structure oriented with the c-axis along the growth direction. The aluminum composition is tuned by changing the power applied to the aluminum target while keeping the power applied to the indium target fixed at 40 W. When increasing the Al content from 0 to 0.39, the room-temperature optical band gap is observed to blue-shift from 1.76 eV to 2.0 eV, strongly influenced by the Burstein–Moss effect. Increasing the substrate temperature, results in an evolution of the morphology from closely-packed columnar to compact. For a substrate temperature of 500 °C and RF power for Al of 150 W, compact Al0.39In0.61N films with a smooth surface (root-mean-square surface roughness below 1 nm) are produced.

Low‐to‐Mid Al Content (x = 0–0.56) AlxIn1−xN Layers Deposited on Si(100) by Radio‐Frequency Sputtering

“…This points out an emission origin related to an energy band of impurities, in agreement with the high carrier concentration measured in the samples. This behavior has been previously observed in both InN and AlInN samples deposited by RF sputtering on sapphire, [10] being attributed to the existence of an important concentration of impurities such as oxygen and nitrogen vacancies in the layers.…”

“…Figure 2a-c shows the 2 Â 2 μm 2 AFM pictographs of these three samples. In addition, as observed in previous results of AlInN alloys deposited by RF sputtering, [10,11] this reduction in the AlInN mosaicity and in the surface roughness with the Al may entail a change in the surface morphology of the samples from closely columnar for InN to compact for Al x In 1Àx N.…”

“…b) Al mole fraction x of the Al x In 1Àx N layers estimated from HRXRD measurements as a function of P Al . The Al mole fraction estimation owns an error bar of %1À4% depending on the Al mole fraction, as obtained by Núñez-Cascajero et al[10] c) Normalized intensity of the rocking curve of the AlInN (0002) diffraction peak versus P Al .…”

“…Our group already has experience on the deposition of In-rich Al x In 1Àx N (x ¼ 0À0.39) on glass, [9] sapphire, [10] and directly on Si(111) [11] substrates, and also with an AlN buffer layer [12] at different temperatures ranging from room temperature [9] to 550 ºC. [10,11] We have achieved high-structural-quality nitride layers on sapphire with a bandgap energy of 1.76À2.03 eV (704À610 nm) and a roomtemperature photoluminescence (PL) emission that blueshifts from 1.59 eV (779 nm) to 1.86 eV (666 nm) for InN and Al 0.36 In 0.64 N, respectively. [10] However, nowadays, the Si technology is based on Si with (100) cubic crystal orientation due to its lower silicon atom density at the surface and amount of dangling bonds that generate undesired recombination centers.…”

“…[10,11] We have achieved high-structural-quality nitride layers on sapphire with a bandgap energy of 1.76À2.03 eV (704À610 nm) and a roomtemperature photoluminescence (PL) emission that blueshifts from 1.59 eV (779 nm) to 1.86 eV (666 nm) for InN and Al 0.36 In 0.64 N, respectively. [10] However, nowadays, the Si technology is based on Si with (100) cubic crystal orientation due to its lower silicon atom density at the surface and amount of dangling bonds that generate undesired recombination centers. [13] So, to adapt the III-nitrides to this technology, we need to develop the growth of Al x In 1Àx N material on Si(100) substrates.…”