Design And Growth Of AlInGaN/AlGaN/GaN Heterostructures

Ga N-based semiconductors material have a large band gap(3.4e V), a very stable chemical property, strong radiation resistance, strong breakdown electric field(5× 106V/cm), high saturated electron transport rate, large thermal conductivity and low dielectric constant. And high electron mobility transistor(HEMT) obtained by III nitride represented Al Ga N/Ga N,the electron mobility at room temperature is very high(>1500cm2/Vs), 2DEG is far beyond(~1×1013cm-2), Al Ga N/Ga N heterostructure made high electron mobility transistor simultaneously with the surface density compared to the other the device. So they has a very broad application prospects in high temperature and microwave power devices. The basic method of conventional Al Ga N/Ga N heterostructure enhancing electrical properties is increasing Al of Al Ga N and make Al Ga N thicker material. but the lattice mismatch between Al Ga N and Ga N can lead to more serious consequences. Based current understanding of the Ga N-based heterostructures and possible developments, the lattice mismatch heterojunction structure adverse two serious effects: first, the lattice mismatch makes the Al Ga N layer have a lot of potential dislocations, which will greatly reduce the crystal quality of the barrier layer and the heterojunction interface, and maybe increase the alloy largely disordered interface roughness, reducing the properties of Al Ga N/Ga N HEMT, which led to greatly reduce of the reliability of the device; two, the piezoelectric effect of Ga N and Al Ga N is obvious presence, prepared using Al Ga N/Ga N high electron mobility structures devices operation, under the direction of a larger gate-drain electric field, resulting in some parts of Al Ga N material, a certain stress. Again due to severe lattice mismatch, the inverse piezoelectric effect in the Al Ga N material strain state will be formed at a high electron mobility while the device is operating and thus it produces defects in the crystal. Defects will lead to reduced reliability of the device.Using Al In N as the barrier layer is a good solution. By adjusting the content of In composition, Al In N and Ga N can be produced almost completely matched a-axis lattice constant in the c plane. However, the presence of gaps in the immiscible phase diagram In N and Al N, results in the growth of Al In N material is subjected, but calculations showthat in all of the III nitride quaternary alloy Al In Ga N has a minimum unstable region, but obtaining high-quality Al In Ga N is very difficult, then this paper design the structure of Al In Ga N/Al Ga N/Ga N to improve the electrical characteristics of the material due to the poor quality of Al In Ga N quaternary alloy.The main work is as follows:1. First of all, optimizing the low temperature Al Ga N/Ga N structure, after then mixed to form a component In to form Al In Ga N/Ga N structure, and the analysis of a low temperature Al Ga N/Ga N structure show that with the decrease of the growth the crystalline quality, the electrical properties of the Al Ga N has very serious deterioration with the decrease of the growth temperature. Then optimizating Al In Ga N/Ga N in lowtemperature. Testing show that, although the crystalline quality and surface morphology of Al In Ga N/Ga N have no improvement compared to Al Ga N/Ga N because of the impact of low temperature, but the electrical properties of Al In Ga N/Ga N has increased, because the lattice mismatch between Al In Ga N and Ga N is much better compared to Al Ga N and Ga N. Maybe the piezoelectric polarization accordingly will be weakened, but strong spontaneous polarization effect is still enough to make heterojunction interface polarization surface charge, and can form a deeper quantum wells. While the lattice mismatch can be reduced to improve the disordered alloy scattering so that the carrier mobility is improved.2. Designing the structure of Al In Ga N/Al Ga N/Ga N to improve the electrical properties of Al In Ga N/Ga N due to poor quality, and successfully carried out Al In Ga N/Al Ga N/Ga N.compared with Al In Ga N/Ga N, the electrical properties of Al In Ga N/Al Ga N/Ga N has been improved, which shows Al Ga N layer is inserted in the middle of Al In Ga N/Ga N heterostructures can effectively improve the electrical properties of Al In Ga N/Ga N structure.