Bandgap bowing parameter and alloy fluctuations for β-(AlxGa1−x)2O3 alloys for x ≤ 0.35 determined from low temperature optical reflectivity

Abstract

A bandgap bowing parameter of 0.4 ± 0.2 eV for β-(AlxGa1−x)2O3 alloys, with Al compositions (x) up to 0.35, has been determined from the bandgap obtained from low temperature optical reflectivity, which suppresses the effect of electron–phonon interaction on the bandgap. A length scale of inhomogeneity of 0.21 ± 0.03 times of the electron–hole mean free path length has been estimated for β-(AlxGa1−x)2O3 alloys. The unit cell of β-(AlxGa1−x)2O3 alloys compresses, and the lattice parameters vary linearly with Al substitution. Our results provide insight into bandgap engineering and alloy disorder for β-(AlxGa1−x)2O3 alloys, which are an important material system for applications in deep ultraviolet opto-electronic devices.

Effect of Al substitution on the electron-phonon interaction for β-Ga2O3

“…A sharp structure around the electronic absorption edge (~4.6 eV) is observed for pure β-Ga 2 O 3 , which arises due to a Van-Hove singularity at around the band gap (~E g ) of a bulk semiconductor. In order to obtain the band gap of β-(Al x Ga 1-x ) 2 O 3 alloy more accurately, the derivative of the OR spectra has been fitted to Aspen's line shape function in the following form [23]:…”

“…Another important application is to escalate its band gap further in the DUV region by substituting the Ga atom with the Al atom. That's why, recently, β-(Al x Ga 1-x ) 2 O 3 alloy has gained paramount attention, as evidenced by the reported literature [14,[21][22][23][24][25][26][27][28][29]. Information regarding electron-phonon (e-ph) interaction strength and mean phonon temperature (θ LO ) can be obtained from the temperature dependence of the bandgap of a semiconductor material.…”

“…There have been a few studies to determine e-ph interaction strength and θ LO from the temperature dependence of the bandgap of β-Ga 2 O 3 [30,31]. However, any report determining e-ph interaction strength and θ LO for β-(Al x Ga 1-x ) 2 O 3 alloys is not available in the literature despite numerous reports for their synthesis as well as other physical properties [14,[21][22][23][24][25][26][27][28][29] This motivates us to estimate θ LO and e-ph interaction strength for the β-(Al x Ga 1-x ) 2 O 3 alloys with different Al compositions. Thus, temperature-dependent (10 to 300 K) optical reflectivity (OR) experiments have been carried out on β-(Al x Ga 1-x ) 2 O 3 alloy samples to obtain bandgap variation with temperature.…”

Electronic structure modification in Fe-substituted β-Ga2O3 from resonant photoemission and soft x-ray absorption spectroscopies

“…It is to be noted that the XRD and UV-VIS-NIR transmission measurements were performed on the β-(Ga 1−x Fe x ) 2 O 3 layers deposited on insulating c-Al 2 O 3 substrates, and the XPS, XAS, and RPES measurements were carried out on β-(Ga 1−x Fe x ) 2 O 3 layers deposited on n-type conducting c-GaN templates (doping density ∼1 × 10 18 cm −3 ). The larger optical bandgap of the c-Al 2 O 3 (8.8 eV) than the c-GaN templates (∼3.4 eV) allows us to determine the optical bandgap of the β-Ga 2 O 3 layers deposited on the c-Al 2 O 3 by employing UV-VIS-NIR transmission spectroscopy [24]. On the other hand, the conducting nature of the c-GaN templates greatly helps to minimize the charging effects due to x-ray exposure during the PES experiments, which otherwise shifts the peak positions and reduces the overall peak intensity.…”

Probing Bond Length and Compositional Disorder in β‐(AlxGa1−x)2O3 Alloys Using Extended X‐Ray Absorption Fine Structure Spectroscopy

“…Another topic of current interest is the Al-substituted β-Ga 2 O 3 ternary alloy, which has the main advantage of tailoring the bandgap further in the DUV region. [17,[21][22][23][24][25] Given the efficient use of an alloy in any device, an in-depth understanding of its local structure upon substitution is quite essential, as a foreign atom distorts the local region around it in the unit cell of the host material. The local distortion may include point defects, clusters of foreign atoms, changes in bond length due to different sizes of the foreign atom, etc.…”