Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userGrowth and Characterization of Metalorganic Vapor-Phase Epitaxy-Grown b{eta}-(AlxGa1-x)2O3/b{eta}-Ga2O3 Heterostructure Channels
208
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report on the growth and characterization of metalorganic vapor-phase epitaxy-grown b{eta}-(AlxGa1-x)2O3/b{eta}-Ga2O3 modulation-doped heterostructures. Electron channel is realized in the heterostructure by utilizing a delta-doped b{eta}-(AlxGa1-x)2O3 barrier. Electron channel characteristics are studied using transfer length method, capacitance-voltage and Hall measurements. Hall sheet charge density of 1.06 x 1013 cm-2 and mobility of 111 cm2/Vs is measured at room temperature. Fabricated transistor showed peak current of 22 mA/mm and on-off ratio of 8 x 106. Sheet resistance of 5.3 k{Omega}/Square is measured at room temperature, which includes contribution from a parallel channel in b{eta}-(AlxGa1-x)2O3.
rate research
Read More
We report on low-temperature MOVPE growth of silicon delta-doped b{eta}-Ga2O3 films with low FWHM. The as-grown films are characterized using Secondary-ion mass spectroscopy, Capacitance-Voltage and Hall techniques. SIMS measurements show that surface segregation is the chief cause of large FWHM in MOVPE-grown films. The surface segregation coefficient (R) is observed to reduce with reduction in the growth temperature. Films grown at 600 {deg}C show an electron concentration of 9.7 x 1012 cm-2 and a FWHM of 3.2 nm. High resolution scanning/transmission electron microscopy of the epitaxial film did not reveal any significant observable degradation in crystal quality of the delta sheet and surrounding regions. Hall measurements of delta-doped film on Fe-doped substrate showed a sheet charge density of 6.1 x 1012 cm-2 and carrier mobility of 83 cm2/V. s. Realization of sharp delta doping profiles in MOVPE-grown b{eta}-Ga2O3 is promising for high performance device applications.
In this work, we have demonstrated wide-composition-range b{eta}-(AlxGa1-x)2O3 thin films with record-high Al compositions up to 77% for b{eta}-(AlxGa1-x)2O3 covering bandgaps from 4.9 to 6.4 eV. With optimized thermal annealing conditions, the b{eta}-Ga2O3 binary thin films on sapphire substrates transformed to the b{eta}-(AlGa)2O3 ternary thin films with different compositions. The binary to ternary transformation resulted from the Al atom diffusion from sapphire into the oxide layers; meanwhile, the Ga atoms diffused into sapphire leading to thicker thin films than the original thicknesses. The interdiffusion processes were confirmed by transmission electron microscopy, which enhanced in proportion to the annealing temperature. The strain states of the b{eta}-(AlGa)2O3 films have been analyzed showing reduced in-plane compressive strain with higher annealing temperature; and the film eventually became strain-free when the temperature was 1400 oC corresponding to the Al composition of 77%. The proposed method is promising for the preparation of the b{eta}-(AlGa)2O3 thin films without employing sophisticated direct-growth techniques for alloys.
Several pn junctions were constructed from mechanically exfoliated ultrawide bandgap (UWBG) beta-phase gallium oxide (b{eta}-Ga2O3) and p-type gallium nitride (GaN). The mechanical exfoliation process, which is described in detail, is similar to that of graphene and other 2D materials. Atomic force microscopy (AFM) scans of the exfoliated b{eta}-Ga2O3 flakes show very smooth surfaces with average roughness of 0.647 nm and transmission electron microscopy (TEM) scans reveal flat, clean interfaces between the b{eta}-Ga2O3 flakes and p-GaN. The device showed a rectification ratio around 541.3 (V+5/V-5). Diode performance improved over the temperature range of 25{deg}C and 200{deg}C, leading to an unintentional donor activation energy of 135 meV. As the thickness of exfoliated b{eta}-Ga2O3 increases, ideality factors decrease as do the diode turn on voltages, tending toward an ideal threshold voltage of 3.2 V as determined by simulation. This investigation can help increase study of novel devices between mechanically exfoliated b{eta}-Ga2O3 and other materials.
High-temperature operation of metal-semiconductor-metal (MSM) UV photodetectors fabricated on pulsed laser deposited b{eta}-Ga2O3 thin films has been investigated. These photodetectors were operated up to 250 {deg}C temperature under 255 nm illumination. The photo current to dark current (PDCR) ratio of about 7100 was observed at room temperature (RT) while it had a value 2.3 at 250 {deg}C at 10 V applied bias. A decline in photocurrent was observed from RT to 150 {deg}C and then it increased with temperature up to 250 {deg}C. The suppression of the blue band was also observed from 150 {deg}C temperature which indicated that self-trapped holes in Ga2O3 became unstable. Temperature-dependent rise and decay times of carriers were analyzed to understand the photocurrent mechanism and persistence photocurrent at high temperatures. Coupled electron-phonon interaction with holes was found to influence the photoresponse in the devices. The obtained results are encouraging and significant for high-temperature applications of b{eta}-Ga2O3 MSM deep UV photodetectors.
High-quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. We report the in-situ metalorganic chemical vapor deposition (MOCVD) of Al$_2$O$_3$ on $beta$-Ga$_2$O$_3$ as a potentially better alternative to the most commonly used atomic layer deposition (ALD). The growth of Al$_2$O$_3$ is performed in the same reactor as Ga$_2$O$_3$ using trimethylaluminum and O$_2$ as precursors without breaking the vacuum at a growth temperature of 600 $^0$C. The fast and slow near interface traps at the Al$_2$O$_3$/ $beta$-Ga$_2$O$_3$ interface are identified and quantified using stressed capacitance-voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (D$_{it}$) are measured using ultra-violet (UV) assisted CV technique. The average D$_{it}$ for the MOSCAP is determined to be 7.8 $times$ 10$^{11}$ cm$^{-2}$eV$^{-1}$. The conduction band offset of the Al$_2$O$_3$/ Ga$_2$O$_3$ interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al$_2$O$_3$/ Ga$_2$O$_3$ interface. The current-voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV/cm. This in-situ Al$_2$O$_3$ dielectric on $beta$-Ga$_2$O$_3$ with improved dielectric properties can enable Ga$_2$O$_3$-based high performance devices.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
