It was reported by Shen et al that the two-dimensional electron gas （2DEG） in an AlGaN/AlN/GaN structure showed high density and improved mobility compared with an AlGaN/GaN structure, but the potential of the AlGaN...It was reported by Shen et al that the two-dimensional electron gas （2DEG） in an AlGaN/AlN/GaN structure showed high density and improved mobility compared with an AlGaN/GaN structure, but the potential of the AlGaN/AlN/GaN structure needs further exploration. By the self-consistent solving of one-dimensional Schroedinger- Poisson equations, theoretical investigation is carried out about the effects of donor density （0-1×10^19 cm^-3） and temperature （50-500 K） on the electron systems in the AlGaN/AlN/GaN and AlGaN/GaN structures. It is found that in the former structure, since the effective △Ec is larger, the efficiency with which the 2DEG absorbs the electrons originating from donor ionization is higher, the resistance to parallel conduction is stronger, and the deterioration of 2DEG mobility is slower as the donor density rises. When temperature rises, the three-dimensional properties of the whole electron system become prominent for both of the structures, but the stability of 2DEG is higher in the former structure, which is also ascribed to the larger effective △Ec. The Capacitance-Voltage （C - V） carrier density profiles at different temperatures are measured for two Schottky diodes on the considered heterostructure samples separately, showing obviously different 2DEG densities. And the temperature-dependent tendency of the experimental curves agrees well with our calculations.展开更多
The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0....The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0.93 eV（C-V） and 0.87 eV（I-V）/1.03 eV（C-V）. However, the BH rises to 0.99 eV（I-V）/1.18 eV（C-V）and then slightly deceases to 0.92 eV（I-V）/1.03 eV（C-V） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung＇s and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.展开更多
文摘It was reported by Shen et al that the two-dimensional electron gas （2DEG） in an AlGaN/AlN/GaN structure showed high density and improved mobility compared with an AlGaN/GaN structure, but the potential of the AlGaN/AlN/GaN structure needs further exploration. By the self-consistent solving of one-dimensional Schroedinger- Poisson equations, theoretical investigation is carried out about the effects of donor density （0-1×10^19 cm^-3） and temperature （50-500 K） on the electron systems in the AlGaN/AlN/GaN and AlGaN/GaN structures. It is found that in the former structure, since the effective △Ec is larger, the efficiency with which the 2DEG absorbs the electrons originating from donor ionization is higher, the resistance to parallel conduction is stronger, and the deterioration of 2DEG mobility is slower as the donor density rises. When temperature rises, the three-dimensional properties of the whole electron system become prominent for both of the structures, but the stability of 2DEG is higher in the former structure, which is also ascribed to the larger effective △Ec. The Capacitance-Voltage （C - V） carrier density profiles at different temperatures are measured for two Schottky diodes on the considered heterostructure samples separately, showing obviously different 2DEG densities. And the temperature-dependent tendency of the experimental curves agrees well with our calculations.
文摘The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0.93 eV（C-V） and 0.87 eV（I-V）/1.03 eV（C-V）. However, the BH rises to 0.99 eV（I-V）/1.18 eV（C-V）and then slightly deceases to 0.92 eV（I-V）/1.03 eV（C-V） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung＇s and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.
