In this study, n-type Al-doped MgxZn1-xO (AMZO) films were deposited onto p-Al0.08Ga0.92N by using radiofrequency
magnetron sputtering followed by annealing at 800°C in nitrogen ambient for 60 s. The film was highly
transparent and had transmittances exceeding 95% in the visible region and a sharp absorption edge visible in the
ultraviolet region. A high leakage current was obtained in the current-voltage (I-V) characteristics of the GMZO/AlGaN
n-p junction diode. The AMZO/AlGaN photodetector based on the AMZO film exhibited a dark current of 1.56 μA at
Vbias = -3V. The peak responsivity of the photodetector was approximately 200 nm and a cutoff wavelength was
observed at approximately 250 nm.
This study investigates the temperature dependence of the current-voltage (I-V) characteristics of Al-doped MgxZn1-xO/p-GaN junction diodes. Specifically, this study reports the deposition of n-type Al-doped MgxZn1-xO (AMZO) films on p-GaN using a radio-frequency (RF) magnetron sputtering system followed by annealing at 700, 800, 900, and 1000 °C in a nitrogen ambient for 60 seconds, respectively. The AMZO/GaN films were thereafter analyzed using Hall measurement and the x-ray diffraction (XRD) patterns. The XRD results show that the diffraction angles of the annealed AMZO films remain the same as that of GaN without shifting. The n-AMZO/p-GaN diode with 900 °C annealing had the lowest leakage current in forward and reverse bias. However, the leakage current of the diodes did not change significantly with an increase in annealing temperatures. These findings show that the n-AMZO/p-GaN junction diode is feasible for GaN-based heterojunction bipolar transistors (HBTs) and UV light-emitting diodes (LEDs).
This study investigates the physical properties of Al-doped MgxZn1-xO (AMZO) films. Al-doped MgxZn1-xO films were deposited by radio-frequency (RF) magnetron sputtering system using a 4 inch ZnO/MgO/Al2O3 (76/19/5 wt%) target. This study determined the resulting x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Hall measurement, and transparent performance of the films. XRD results indicate that the diffraction angles of the annealed AMZO film shifted toward the high-angle side, indicating that thermal annealing could relax the compressive strain components in the as-deposited samples. XPS results reveal a high carbon content on the surface of MgxZn1-xO. This may be due to contamination. The average Mg content of the as-grown AMZO is about 19.23 at. % at a depth of 40 nm. The Al-doped MgxZn1-xO film in this study shows high transparency with transmittances over 95 % in the visible region (400 ~ 800nm), and a sharp absorption edge is visible in the UV region due to the Mg content. The Hall measurement of Al-doped MgxZn1-xO films deposited at lower RF power show higher doping concentrations, lower resistivity and higher mobility as a function of the annealing temperature. Experimental results indicate that Al-doped MgxZn1-xO film with 1000 °C annealing contains more oxygen vacancies, which play the role of donor. Oxygen vacancies generate states in the band gap and increase conductivity.
This work investigates the physical properties of the MgxZn1-xO films. MgxZn1-xO films were deposited by RF
magnetron sputtering system using a 6 inch ZnO/MgO (80/20 wt%) target. The XPS, Hall measurement, and transparent
performance are measured. The XPS results show that there is high Carbon element content on the surface of MgxZn1-xO
maybe due to the contamination and the average of the Mg content is about 25 at. %. The XRD results indicate that the
appearance of only (111) peaks for as-grown MgxZn1-xO film is a sign of the cubic single phase. In this study, the
MgxZn1-xO film show high transparency with transmittances over 90 % in the visible region (400 ~ 700nm) and the sharp
absorption edge is visible in UV region due to the Mg content. Therefore, the Hall measurement of MgxZn1-xO films
which were deposited at lower RF power show the higher doping concentration, the lower resistivity and higher mobility
as a function of the annealing temperatures. The experimental results indicate that MgxZn1-xO film with 800 °C
annealing contains more oxygen vacancies which play the role of donor. Since oxygen vacancies generate states in the
band gap and cause an increase in conductivity.
This work investigates the reactive ions etching (RIE) physical properties of n-type ZnO using H2/CH4 and H2/CH4/Ar
mixtures by varying the gas flow ratio, the radio-frequency (rf) plasma power and the chamber pressure. Atomic force
microscopy (AFM) results and surface topographies are discussed. Although the etching rate of the n-ZnO at an H2/CH4
flow rate of 100/0 sccm, a work pressure of 100 mTorr and an rf power of 300 W is lower than under any other
conditions, the rms roughness of 43.78 nm is the highest, and supports the application of roughened transparent contact
layer (TCL) in light-emitting diodes (LEDs). The dynamics associated with the high etching rate were highly efficient at
an H2/CH4/Ar flow rate of 38/5/57 sccm, a work pressure of 150 mTorr and an rf power of 300 W. In addition, the ZnO
with thermal annealing were studied. The slower etching rate of annealed n-ZnO is observed due to an increase the
crystal quality of the ZnO films after thermal annealing which consists with the x-ray diffraction (XRD) results.
We have investigated the thermal stability of three composite metals on their contact resistivities and luminous intensities for using as the reflector in flip-chip light-emitting diode (FCLED). The composite metals were simultaneously deposited on n-type GaN without alloy to form n-type Ohmic contact and simplify the process. The investigated composite metals were Ti/Al/Ti/Au (30/500/30/300 nm), Cr/Al/Cr/Au (30/500/30/300 nm) and Cr/Ti/Au (500/30/300 nm), respectively. The specific contact resistivity of Ti/Al/Ti/Au, Cr/Al/Cr/Au and Cr/Ti/Au on the n-type GaN Ohmic contact were changed from 5.4×10-4, 6.6×10-4 and 7.7×10-4 Ω-cm2 to 5.3×10-4, 4.5×10-4 and 1.3×10-4 Ω-cm2 respectively after 500 hours thermal stress at 150°C in the air. After 96 hours of thermal stress, the luminous intensities at 20 mA of these three structures were decreased 6.2%, 11.1% and 1.4%, respectively. Therefore, in addition to maintain good n-type ohmic contact and simplify the process, the Cr/Ti/Au composite metal demonstrates good thermal stability as a reflector in FCLED.
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