An approach of growing crack-free GaN-based InGaN-multiple quantum wells (MQWs) with emission at 365 nm on AlN template, instead of conventional GaN template, by metal-organic chemical vapor deposition is presented. The AlN template used here was grown on the vicinal 2° misoriented sapphire substrate. Scanning electron microscopy and atomic force microscopy investigation show that cracks do not form in the MQWs structure grown on an AlN template. The full width at half maximum of high resolution X-ray diffraction rocking curve of the n-Al_0.02Ga_0.98N buffer decreases dramatically when grown on an AlN template, indicating improved crystalline quality. Moreover, Photoluminescence spectra show that the employment of AlN/2° misoriented sapphire template is beneficial to internal quantum efficiency and its thermal stability. Finally, transmission election microscopy reveals a prominent reduction of dislocation density at the undoped GaN/AlN interface.

X. M. Fan;J. C. Bai;S. R. Xu;进成 张;培咸 李;R. S. Peng;Y. Zhao;J. J. Du;X. F. Shi;跃 郝

Thin Solid Films

2018-10-1

The breakdown characteristics of thin gate oxide were tested under constant current stresses, The breakdown theory of time-dependent dielectric breakdown was researched. The effects of the area of gate oxide on the breakdown characteristics were discussed. The charge to breakdown Q_BD is dependent on the stressed current density and the area of gate oxide. An analytical expression of Q_BD was deduced and relative parameters were presented.

红侠 刘;跃 郝

Pan Tao Ti Hsueh Pao/Chinese Journal of Semiconductors

2000-2

Breakdown character of thin SiO₂ is investigated by using substrate hot-carrier injection techniques. Hot-carrier induced thin gate oxide damaged shows different breakdown character compared with the case of conventional F-N tunneling experiments. Good correlation between the calculated electron energy in the oxide and the electric field in the silicon substrate suggests that the difference between hot-electron injection and the F-N tunneling can be explained in terms of the average electron energy in the oxide. Hot holes injection experiments reveal that the life of oxide breakdown is not simply determined by the total number of injected holes. New hot-carrier-induced TDDB (Time-dependent dielectric breakdown) models of thin gate oxide are reported in this paper.

红侠 刘;Jian Ping Fang;跃 郝

Wuli Xuebao/Acta Physica Sinica

2001-6

With the fast development of the perovskite solar cell, its energy conversion efficiency has improved rapidly. In this paper, a CH₃NH₃PbI_3-xCl_x organic-inorganic perovskite solar cell (PSC) was successfully prepared by the one-step solvent engineering method, and the planar heterojunction perovskite solar cell was optimized by interface engineering of the cathode interlayers. It was found that TiCl₄ treatment could effectively reduce the TiO₂ surface roughness, decrease the surface defects, improve the perovskite thin film crystallinity, and reduce the charge carrier recombination; hence, the short-circuit current density of PSCs and charge extraction and collection efficiencies were enhanced. Furthermore, PC₆₀BM fullerene treatment could optimize the contact condition and reduce the interfacial potential loss. The device hysteresis effects after PCBM treatment were also reduced. The combination of TiCl₄ and PC₆₀BM treatments could largely improve the PSC device performance with a power conversion efficiency of 16.4% due to the synergetic effect.

Jing Ma;Jingjing Chang;Zhenhua Lin;Xing Guo;Long Zhou;Ziye Liu;He Xi;Dazheng Chen;Chunfu Zhang;跃 郝

Journal of Physical Chemistry C

2018-1-18

We have developed a novel AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using stack gate HfO₂/Al ₂O₃ structure grown by atomic layer deposition (ALD). The stack gate consists of a thin Hf0₂ (30Å) gate dielectric and a thin A1₂O₃ (20Å) interfacial passivation layer (TPL). For the 50Å stack gate, no measurable C-V hysteresis and smaller threshold voltage shift were observed, indicating that a high quaity interface can be achieved using a A1₂O₃ IPL on AlGaN substrate. Good surface passivation effects of the A1₂O₃ IPL have also been confirmed by pulsed gate measurements. Devices with 1-μm gate lengths exhibit a cutoff frequency (f_T) of 12GHz and a maximum frequency of oscillation (f_MAx) of 34GHz. The gate leakage current is at least six orders of magnitude lower than that of the reference HEMTs at positive gate bias.

Yuan Zheng Yue;跃 郝;进成 张

2008

High quality InAlN/InGaN/InAlN/InGaN double channel heterostructures were proposed and grown by metal organic chemical vapor deposition. Benefiting from the adoption of the pulsed growth method and Two-Step AlN interlayer, the material quality and interface characteristics of the double channel heterostructures are satisfactory. The results of the temperature-dependent Hall effect measurement indicated that the transport properties of the double channel heterostructures were superior to those of the traditional single channel heterostructures in the whole test temperature range. Meanwhile, the sheet resistance of the double channel heterostructures reached 218.5 Ω/□ at 300 K, which is the record of InGaN-based heterostructures. The good transport properties of the InGaN double channel heterostructures are beneficial to improve the performance of the microwave power devices based on nitride semiconductors.

Yachao Zhang;Zhizhe Wang;Shengrui Xu;Dazheng Chen;为民 包;金风 张;进成 张;跃 郝

Applied Physics Letters

2017-11-27

An enhanced InGaN/GaN multiple-quantum-well (MQW) solar cell was produced and characterized through the superlattice structure (SLS) insertion. The experiments demonstrated that the conversion efficiency of the fabricated device increased from 0.61 to 1.61%, compared to the device without SLS. The promising result was considered to originate from the SLS insertion. From Raman analysis and theoretical calculation of the electron transmissivity, it was demonstrated that the plane strain of GaN was effectively released when the SLS was inserted and the electron tunneling effect was enhanced. Consequently, the collection of photo-generated electrons was strengthened, which thereby led to the conversion efficiency increase.

Hengsheng Shan;Bin Chen;Xiaoya Li;Zhiyu Lin;Shengrui Xu;跃 郝;进成 张

Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes

2017-11

In this study, we report on the crystal quality of InGaN epifilms with different indium fractions grown at different growth temperatures on c-plane sapphire substrates with an AlN nucleation layer by using low-pressure metal-organic chemical-vapor deposition (MOCVD). High-resolution X-ray diffraction (HRXRD), atom force microscopy (AFM), photoluminescence (PL) and Raman scattering measurements were employed to study the crystal quality, optical properties and strain condition of InGaN epifilms with increasing indium fraction (from 4. 36% to 15. 36%). Results show that InGaN epitaxial layers can be realized with a higher indium fraction at a lower temperature by inserting an AlN nucleation layer between the sapphire substrate and the GaN buffer layer and that the obtained InGaN epifilms have an improved crystal quality and a lower threading dislocation density.

Dang Hui Wang;Sheng Rui Xu;进成 张;Ke Chen;Zhi Wei Bi;Lin Xia Zhang;Fan Na Meng;Shan Ai;跃 郝

Journal of the Korean Physical Society

2012-8

An InGaN/GaN solar cell including a dual multiple quantum wells (MQWs) structure is investigated. It shows an obvious advantage over the conventional InGaN/GaN cell, which only contains a single MQWs structure. Because the short current density (J_sc) increases, the 1 sun power conversion efficiency significantly improves from 0.62% (single MQWs cell) to 1.02% (dual MQWs cell). From the measurement of EQE and PL spectra, the enhancement of effective photoelectric response within the solar spectrum mainly contributes to the high device performance, due to the introduced upper MQWs of higher In content.

Zhen Bi;进成 张;Qiye Zheng;Ling Lv;Zhiyu Lin;Hengsheng Shan;培咸 李;Xiaohua Ma;Yiping Han;跃 郝

IEEE Photonics Technology Letters

2016-10-15

The behavior of Schottky contacts in AlGaN/GaN high electron mobility transistors (HEMTs) is investigated by temperature-dependent current - voltage (T - I - V) measurements from 300 K to 473 K. The ideality factor and barrier height determined based on the thermionic emission (TE) theory are found to be strong functions of temperature, while present a great deviation from the theoretical value, which can be expounded by the barrier height inhomogeneities. In order to determine the forward current transport mechanisms, the experimental data are analyzed using numerical fitting method, considering the temperature-dependent series resistance. It is observed that the current flow at room temperature can be attributed to the tunneling mechanism, while thermionic emission current gains a growing proportion with an increase in temperature. Finally, the effective barrier height is derived based on the extracted thermionic emission component, and an evaluation of the density of dislocations is made from the I - V characteristics, giving a value of 1.49 × 10⁷ cm^-2.

Mei Wu;Da Yong Zheng;Yuan Wang;Wei Wei Chen;Kai Zhang;Xiao Hua Ma;进成 张;跃 郝

Chinese Physics B

2014