通过自洽求解二维泊松方程和薛定谔方程发现栅-漏间隙中的强场峰两侧的异质结能带产生巨大畸变,使部分二维电子气不能通过强场峰而形成局域电子气。从电子气补偿效应出发研究了外沟道夹断前后的沟道电阻变化。研究了从外沟道渗透到内沟...通过自洽求解二维泊松方程和薛定谔方程发现栅-漏间隙中的强场峰两侧的异质结能带产生巨大畸变,使部分二维电子气不能通过强场峰而形成局域电子气。从电子气补偿效应出发研究了外沟道夹断前后的沟道电阻变化。研究了从外沟道渗透到内沟道的电场梯度和缓冲层沟道阱,发现了新的电场梯度引起的能带下弯(Electric field gradient induced band bowing,EFGIBB)效应。从漏电压引起的电势下降(Drain-induced barrier lowering,DIBL)和EFGIBB两效应出发建立起新的穿通阱模型,由此解释了实验中观察到的各类阈值电压负移、亚阈值电流和穿通等沟道夹断以后的行为,发现了由强负栅压引起的新穿通现象。最后讨论了新穿通行为对器件性能的影响,探索优化设计器件结构,改善器件性能的新途径。展开更多
Thick GaN films were grown on GaN/sapphire template in a vertical HVPE reactor. Various material characterization techniques,including AFM, SEM, XRD, RBS/Channeling, CL, PL, and XPS, were used to characterize these Ga...Thick GaN films were grown on GaN/sapphire template in a vertical HVPE reactor. Various material characterization techniques,including AFM, SEM, XRD, RBS/Channeling, CL, PL, and XPS, were used to characterize these GaN epitaxial films. It was found that stepped/terraced structures appeared on the film surface,which were indicative of a nearly step-flow mode of growth for the HVPE GaN despite the high growth rate. A few hexagonal pits appeared on the surface, which have strong light emission. After being etched in molten KOH, the wavy steps disappeared and hexagonal pits with {1010} facets appeared on the surface. An EPD of only 8 ×10^6cm^-2 shows that the GaN film has few dislocations. Both XRD and RBS channeling indicate the high quality of the GaN thick films. Sharp band-edge emission with a full width at half maximum（FWHM）of 67meV was observed, while the yellow and infrared emissions were also found. These emissions are likely caused by native defects and C and O impurities.展开更多
The subband structures, distributions of electron and hole wave functions, state density, optical gain spectra, and transparency carrier density of the V-groove Zn 1-x Cd x Se/ZnSe quantum wires are investigated theor...The subband structures, distributions of electron and hole wave functions, state density, optical gain spectra, and transparency carrier density of the V-groove Zn 1-x Cd x Se/ZnSe quantum wires are investigated theoretically using four band effective-mass Hamiltonian, which takes into account the effects of the valence band anisotropy and the band mixing. The biaxial strain effect for quantum wires is included in the calculation. The compressive strain in the Zn 1-x Cd x Se wire region increases the energy separation between the uppermost subbands. The optical gain with xy -polarized light is enhanced, while optical gain with z -polarized light is strongly decreased. The xy -polarized optical gain spectrum has a peak at around 2.541 eV, with the transparency carrier density of 0.75×10 18 cm -3 . The calculated results also show that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.展开更多
文摘通过自洽求解二维泊松方程和薛定谔方程发现栅-漏间隙中的强场峰两侧的异质结能带产生巨大畸变,使部分二维电子气不能通过强场峰而形成局域电子气。从电子气补偿效应出发研究了外沟道夹断前后的沟道电阻变化。研究了从外沟道渗透到内沟道的电场梯度和缓冲层沟道阱,发现了新的电场梯度引起的能带下弯(Electric field gradient induced band bowing,EFGIBB)效应。从漏电压引起的电势下降(Drain-induced barrier lowering,DIBL)和EFGIBB两效应出发建立起新的穿通阱模型,由此解释了实验中观察到的各类阈值电压负移、亚阈值电流和穿通等沟道夹断以后的行为,发现了由强负栅压引起的新穿通现象。最后讨论了新穿通行为对器件性能的影响,探索优化设计器件结构,改善器件性能的新途径。
文摘Thick GaN films were grown on GaN/sapphire template in a vertical HVPE reactor. Various material characterization techniques,including AFM, SEM, XRD, RBS/Channeling, CL, PL, and XPS, were used to characterize these GaN epitaxial films. It was found that stepped/terraced structures appeared on the film surface,which were indicative of a nearly step-flow mode of growth for the HVPE GaN despite the high growth rate. A few hexagonal pits appeared on the surface, which have strong light emission. After being etched in molten KOH, the wavy steps disappeared and hexagonal pits with {1010} facets appeared on the surface. An EPD of only 8 ×10^6cm^-2 shows that the GaN film has few dislocations. Both XRD and RBS channeling indicate the high quality of the GaN thick films. Sharp band-edge emission with a full width at half maximum（FWHM）of 67meV was observed, while the yellow and infrared emissions were also found. These emissions are likely caused by native defects and C and O impurities.
文摘The subband structures, distributions of electron and hole wave functions, state density, optical gain spectra, and transparency carrier density of the V-groove Zn 1-x Cd x Se/ZnSe quantum wires are investigated theoretically using four band effective-mass Hamiltonian, which takes into account the effects of the valence band anisotropy and the band mixing. The biaxial strain effect for quantum wires is included in the calculation. The compressive strain in the Zn 1-x Cd x Se wire region increases the energy separation between the uppermost subbands. The optical gain with xy -polarized light is enhanced, while optical gain with z -polarized light is strongly decreased. The xy -polarized optical gain spectrum has a peak at around 2.541 eV, with the transparency carrier density of 0.75×10 18 cm -3 . The calculated results also show that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.
