The
This content will become publicly available on July 18, 2023
- Award ID(s):
- 1809077
- Publication Date:
- NSF-PAR ID:
- 10346390
- Journal Name:
- Journal of Physics D: Applied Physics
- Volume:
- 55
- Issue:
- 39
- Page Range or eLocation-ID:
- 395101
- ISSN:
- 0022-3727
- Sponsoring Org:
- National Science Foundation
More Like this
-
β -Ga2O3nanomembrane (NM)/diamond heterostructure is one of the promising ultra-wide bandgap heterostructures that offers numerous complementary advantages from both materials. In this work, we have investigated the thermal properties of theβ -Ga2O3NM/diamond heterostructure with three different thicknesses ofβ -Ga2O3nanomembranes (NMs), namely 100 nm, 1000 nm, and 4000 nm thickβ -Ga2O3NMs using Raman thermometry. The thermal property—temperature relationships of theseβ -Ga2O3NM/diamond heterostructures, such as thermal conductivity and interfacial thermal boundary conductance were determined under different temperature conditions (from 100 K to 500 K with a 40 K interval). The result provides benchmark knowledge about the thermal conductivity ofβ -Ga2O3NMs over a wide temperature range for the design of novelβ -Ga2O3-based power electronics and optoelectronics. -
In this work, the structural and electrical properties of metalorganic chemical vapor deposited Si-doped β-(Al x Ga 1−x ) 2 O 3 thin films grown on (010) β-Ga 2 O 3 substrates are investigated as a function of Al composition. The room temperature Hall mobility of 101 cm 2 /V s and low temperature peak mobility (T = 65 K) of 1157 cm 2 /V s at carrier concentrations of 6.56 × 10 17 and 2.30 × 10 17 cm −3 are measured from 6% Al composition samples, respectively. The quantitative secondary ion mass spectroscopy (SIMS) characterization reveals a strong dependence of Si and other unintentional impurities, such as C, H, and Cl concentrations in β-(Al x Ga 1−x ) 2 O 3 thin films, with different Al compositions. Higher Al compositions in β-(Al x Ga 1−x ) 2 O 3 result in lower net carrier concentrations due to the reduction of Si incorporation efficiency and the increase of C and H impurity levels that act as compensating acceptors in β-(Al x Ga 1−x ) 2 O 3 films. Lowering the growth chamber pressure reduces Si concentrations in β-(Al x Ga 1−x ) 2 O 3 films due to the increase of Al compositions as evidenced by comprehensive SIMS and Hallmore »
-
Abstract In this work, we report a simplified method to measure thermal conductivity from the typical Raman thermometry method by employing a much simpler dispersion relationship equation and the Debye function, instead of solving the heat equation. Unlike the typical Raman thermometry method, our new method only requires monitoring of the temperature-dependent Raman mode shifting without considering laser power-dependent Raman mode shifting. Thus, this new calculation method offers a simpler way to calculate the thermal conductivity of materials with great precision. As a model system, the
β -Ga2O3nanomembrane (NM) on a diamond substrate was prepared to measure thermal conductivity ofβ -Ga2O3NMs at different thicknesses (100 nm, 1000 nm, and 4000 nm). Furthermore, the phonon penetration depth was investigated to understand how deep phonons can be dispersed in the sample so as to guide the dimensional design parameter of the device from the thermal management perspective. -
In this paper, we demonstrated large-size free-standing single-crystal β-Ga 2 O 3 NMs fabricated by the hydrogen implantation and lift-off process directly from MOCVD grown β-Ga 2 O 3 epifilms on native substrates. The optimum implantation conditions were simulated with a Monte-Carlo simulation method to obtain a high hydrogen concentration with a narrow ion distribution at the desired depth. Two as grown β-Ga 2 O 3 samples with different orientations ([100] and [001]) were used to successfully create 1.2 μm thick β-Ga 2 O 3 NMs without any physical damage. These β-Ga 2 O 3 NMs were then transfer-printed onto rigid and flexible substrates such as SiC and polyimide substrates. Various material characterization studies were performed to investigate their crystal quality, surface morphologies, optical properties, mechanical properties, and bandgaps before and after the lift-off and revealed that the good material quality was maintained. This result offers several benefits in that the thickness, doping, and size of β-Ga 2 O 3 NMs can be fully controlled. Moreover, more advanced β-Ga 2 O 3 -based NM structures such as (Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 heterostructure NMs can be directly created from their bulk epitaxy substrates;more »
-
This paper reports the fabrication of β-Ga 2 O 3 nanomembrane (NM) based flexible photodetectors (PDs) and the investigation of their optoelectrical properties under bending conditions. Flexible β-Ga 2 O 3 NM PDs exhibited reliable solar-blind photo-detection under bending conditions. Interestingly, a slight shifting in wavelength of the maximum solar-blind photo-current was observed under the bending condition. To investigate the reason for this peak shifting, the optical properties of β-Ga 2 O 3 NMs under different strain conditions were measured, which revealed changes in the refractive index, extinction coefficient and bandgap of strained β-Ga 2 O 3 NMs due to the presence of nano-sized cracks in the β-Ga 2 O 3 NMs. The results of a multiphysics simulation and a density-functional theory calculation for strained β-Ga 2 O 3 NMs showed that the conduction band minimum and the valence band maximum states were shifted nearly linearly with the applied uniaxial strain, which caused changes in the optical properties of the β-Ga 2 O 3 NM. We also found that nano-gaps in the β-Ga 2 O 3 NM play a crucial role in enhancing the photoresponsivity of the β-Ga 2 O 3 NM PD under bending conditions due to the secondarymore »