Characteristics of GaN materials

wallpapers Industry 2021-04-01
The research and application of gallium nitride material is the frontier and hot spot of global semiconductor research. It is a new type of semiconductor material for the development of microelectronic devices and optoelectronic devices. Together with semiconductor materials such as SIC and diamond, it is known as the successor to the first generation of Ge, Si semiconductor materials, second-generation GaAs, InP compound semiconductor materials after the third-generation semiconductor materials. It has a wide direct bandgap, strong atomic bonds, high thermal conductivity, good chemical stability (hardly corroded by any acid), and strong anti-radiation ability. It is used in optoelectronics, high temperature, and high power devices, and high There are broad prospects in the application of high-frequency microwave devices.
Gallium nitride is an extremely stable compound and a hard, high melting point material with a melting point of about 1700°C. Gallium nitride has a high degree of ionization, which is the highest (0.5 or 0.43) among the III-V group compounds. Under atmospheric pressure, gallium nitride crystals generally have a hexagonal wurtzite structure. It has 4 atoms in a cell, and the atomic volume is about half of GaAs. Because of its high hardness, it is also a good coating protection material.
Chemical properties
At room temperature, gallium nitride is insoluble in water, acids, and alkalis, but dissolves at a very slow rate in hot alkaline solutions. NaOH, H2SO4, and H3PO4 can corrode poor quality gallium nitride quickly and can be used for defect detection of these low-quality gallium nitride crystals. Gallium nitride exhibits unstable characteristics at high temperatures under HCL or H2 gas and is most stable under N2 gas.
Structural characteristics
There are two main crystal structures of GaN, namely wurtzite structure and sphalerite structure.
Electrical characteristics
The electrical characteristics of GaN are the main factors affecting the device. Unintentionally doped GaN is n-type in all cases, and the electron concentration of the best sample is about 4×1016/cm3. In general, the prepared P-type samples are highly compensated.
Many research groups have been engaged in this area of ​​research. Among them, Nakamura reported that the highest GaN mobility data is μn=600cm2/v·s and μn=1500cm2/v·s at room temperature and liquid nitrogen temperature, respectively, and the corresponding current-carrying The sub-concentrations are n=4×1016/cm3 and n=8×1015/cm3. The electron concentration values ​​of MOCVD deposited GaN layers reported in recent years are 4×1016/cm3, <1016/cm3; the results of plasma-activated MBE are 8×103/cm3, <1017/cm3.
The concentration of undoped carriers can be controlled in the range of 1014-1020/cm3. In addition, through the P-type doping process and Mg low-energy electron beam irradiation or thermal annealing treatment, the doping concentration can be controlled in the range of 1011-1020/cm3.
Optical properties
The characteristics of GaN that people pay attention to are aimed at its application in blue and violet light-emitting devices. Maruska and Tietjen first accurately measured the direct gap energy of GaN as 3.39 eV. Several groups have studied the dependence of the GaN bandgap on temperature. Pankow et al. estimated an empirical formula for the temperature coefficient of the bandgap: dE/DT = -6.0×10-4eV/k. Montemar measured the basic bandgap as 3.503eV±0.0005eV, Eg=3.503+(5.08×10-4T2)/(T-996) eV at 1.6kT.
In addition, many people are studying the optical properties of gallium nitride.