高压开关AlGaN/GaN HEMT材料及器件研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

GaN/AlGaN基紫外探测器研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

GaN 基垂直腔面发射激光器研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-08T13:07:49Z No. of bitstreams: 1 张江勇毕业论文.pdf: 1659784 bytes, checksum: eb70417dd2986217af3eaaba001bc8fd (MD5)

微纳光学结构增强GaN LED出光效率研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-13T08:02:10Z No. of bitstreams: 1 博士毕业论文_刘宏伟.pdf: 3404178 bytes, checksum: e5e1511387570aa5c92a4cc48df47e81 (MD5)

高功率GaN基激光器列阵的工艺制作和特性研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-13T08:09:45Z No. of bitstreams: 1 季 莲--高功率GaN基激光器列阵的工艺制作和特性研究.pdf: 2893344 bytes, checksum: 91687f7e5453fbcf7e91203e116a216e (MD5)

基于横向外延生长的GaN LED 特性研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-13T08:18:55Z No. of bitstreams: 1 毕业论文_王良吉.pdf: 5299270 bytes, checksum: 6b0aeaa63a52321331f321143a5b0a09 (MD5)

Study of GaN epilayers growth on freestanding Si cantilevers

Five-micron thick freestanding Si cantilevers were fabricated on bulk Si (1 1 1) substrates with surface/bulk micromachining (SBM) process. Then 1-mu m thick GaN layers were deposited on the Si cantilevers by metal-organic chemical vapor deposition (MOCVD). Epilayers on cantilever areas were obtained crack-free, and the photoluminescence (PL) spectra verified the stress reduction and better material quality in these suspended parts of GaN. Back sides of the cantilevers were also covered with GaN layers, which prevented the composite beams from bending dramatically. This paper had proved the feasibility of integrating high-quality GaN epilayers with Si micromechanical structures to realize GaN-based micro electro-mechanical system (MEMS). (C) 2009 Elsevier Ltd. All rights reserved.

An experimental study about the influence of well thickness on the electroluminescence of InGaN/GaN multiple quantum wells

The influence of well thickness on the electroluminescence (EL) of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition is investigated. It is found that the peak wavelength of EL increases with the increase of well thickness when the latter is located in the range of 3.0-5.1 nm. The redshift is mainly attributed to the quantum confined Stark effect (QCSE). As a contrast, it is found that the EL intensity of InGaN/GaN MQWs increases with the increase of well thickness in spite of QCSE. The result of X-ray diffraction demonstrates that the interface become smoother with the increase of well thickness and suggests that the reduced interface roughness can be an important factor leading to the increase of EL intensity of InGaN/GaN MQWs. (C) 2009 Elsevier B.V. All rights reserved.

Effect of surface treatment of GaN based light emitting diode wafers on the leakage current of light emitting diode devices

To form low-resistance Ohmic contact to p-type GaN, InGaN/GaN multiple quantum well light emitting diode wafers are treated with boiled aqua regia prior to Ni/Au (5 nm/5 nm) film deposition. The surface morphology of wafers and the current-voltage characteristics of fabricated light emitting diode devices are investigated. It is shown that surface treatment with boiled aqua regia could effectively remove oxide from the surface of the p-GaN layer, and reveal defect-pits whose density is almost the same as the screw dislocation density estimated by x-ray rocking curve measurement. It suggests that the metal atoms of the Ni/Au transparent electrode of light emitting diode devices may diffuse into the p-GaN layer along threading dislocation lines and form additional leakage current channels. Therefore, the surface treatment time with boiled aqua regia should not be too long so as to avoid the increase of threading dislocation-induced leakage current and the degradation of electrical properties of light emitting diodes

Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer

We present the growth of GaN epilayer on Si (111) substrate with a single AlGaN interlayer sandwiched between the GaN epilayer and AlN buffer layer by using the metalorganic chemical vapour deposition. The influence of the AlN buffer layer thickness on structural properties of the GaN epilayer has been investigated by scanning electron microscopy, atomic force microscopy, optical microscopy and high-resolution x-ray diffraction. It is found that an AlN buffer layer with the appropriate thickness plays an important role in increasing compressive strain and improving crystal quality during the growth of AlGaN interlayer, which can introduce a more compressive strain into the subsequent grown GaN layer, and reduce the crack density and threading dislocation density in GaN film.

Hole concentration test of p-type GaN by analyzing the spectral response of p-n(+) structure GaN ultraviolet photodetector

A new method to test the hole concentration of p-type GaN is proposed, which is carried out by analyzing the spectral response of p-n(+) structure GaN ultraviolet photodetector. It is shown that the spectral response of the photodetector changes considerably with reversed bias. It is found that the difference between photodetector's quantum efficiency at two wavelengths, i.e. 250 and 361 nm, varies remarkably with increasing reversed bias. According to the simulation calculation, the most characteristic change occurs at a reversed voltage under which the p-GaN layer starts to be completely depleted. Based on this effect the carrier concentration of p-GaN can be derived.

Ferromagnetic modification of GaN film by Cu+ ions implantation

The structural and magnetic properties of Cu+ ions-implanted GaN films have been reported. Eighty kilo-electron-volt Cu+ ions were implanted into n-type GaN film at room temperature with fluences ranging from 1 x 10(16) to 8 x 10(16) cm(-2) and subsequently annealed at 800 degrees C for 1 h in N-2 ambient. PIXE was employed to determine the Cu-implanted content. The magnetic property was measured by the Quantum Design MPMS SQUID magnetometer. No secondary phases or clusters were detected within the sensitivity of XRD. Raman spectrum measurement showed that the Cu ions incorporated into the crystal lattice positions of GaN through substitution of Ga atoms. Apparent ferromagnetic hysteresis loops measured at 10 K were presented. The experimental result showed that the ferromagnetic signal strongly increased with Cu-implanted fluence from 1 x 10(16) to 8 x 10(16) cm(-2).

Structural and optical properties of Al1-xInxN epilayers on GaN template grown by metalorganic chemical vapor deposition

This paper reports that Al1-xInxN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%-20%. X-ray diffraction results indicate that all these Al1-xInxN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al1-xInxN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al1-xInxN epilayers. A bowing parameter of 6.5 eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al1-xInxN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al1-xInxN sample.

Effects of AlGaN/AlN Stacked Interlayers on GaN Growth on Si (111)

We report the growth of high quality and crack-free GaN film on Si (111) substrate using Al0.2Ga0.8N/AlN stacked interlayers. Compared with the previously used single AlN interlayer, the AlGaN/AlN stacked interlayers can more effectively reduce the tensile stress inside the GaN layer. The cross-sectional TEM image reveals the bending and annihilation of threading dislocations (TDs) in the overgrown GaN film which leads to a decrease of TD density.

Carrier capture by threading dislocations in (In,Ga)N/GaN heteroepitaxial layers

Using spatially resolved cathodoluminescence spectroscopy, we investigate the spatial luminescence distribution in a fully strained (In,Ga)N layer, in particular, its correlation with the distribution of threading dislocations (TDs). Regarding the impact of TDs on the luminescence properties, we can clearly distinguish between pure edge-type TDs and TDs with screw component. At the positions of both types of TDs, we establish nonradiative recombination sinks. The radius for carrier capture is at least four times larger for TDs with screw component as for pure edge-type TDs. The large capture radius of the former is due to a spiral-like growth mode resulting in an increase in the In content in the center of the spiral domains in comparison to their periphery.