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Stability and electronic structure studies of LaAlO_3/SrTiO_3 (110) heterostructures

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Chinese Physics B 2014年第8期23卷 468-473页

作者：杜颜伶王春雷李吉超徐攀攀张新华刘剑苏文斌梅良模 School of Physics State Key Laboratory of Crystal Materials Shandong University College of Science and Technology Shandong University of Traditional Chinese Medicine

The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAIO3/SrTiO3 （110）. By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAIO3/SrTiO3 （110） heterostructure, the Ti-O octahedron distortions cause the Ti tzg orbitals to split into the two- fold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaA103 and SrTiO3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAIO3/SrTiO3 （110）.

关键词： two-dimensional electron gas LaAIO3/SrTiO3 (110) interface magnetic interface

Characterization of a room temperature terahertz detector based on a GaN/AlGaN HEMT

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Journal of Semiconductors 2011年第6期32卷 40-43页

作者：周宇孙建东孙云飞张志鹏林文魁刘宏欣曾春红陆敏蔡勇吴东岷楼柿涛秦华张宝顺 Key Laboratory of Nanodevices Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of Sciences

We report on the characterization of a room temperature terahertz detector based on a GaN/AlGaN high electron mobility transistor integrated with three patch *** results prove that both horizontal and perpendicular electric fields are induced in the electron channel.A photocurrent is generated when the electron channel is strongly modulated by the gate *** the large channel length and gate-source/drain distance, significant horizontal and perpendicular fields are *** device is well described by the self-mixing of terahertz fields in the electron *** noise-equivalent power and responsivity are estimated to be 100 nW/（Hz）^（1/2） and 3 mA/ W at 292 K,*** decrease in responsivity is observed up to a modulation frequency of 5 kHz. The detector performance can be further improved by engineering the source-gate-drain geometry to enhance the nonlinearity.

关键词： terahertz detector high electron mobility transistor mixing two-dimensional electron gas

Growth condition optimization and mobility enhancement through prolonging the GaN nuclei coalescence process of AlGaN/AlN/GaN structure

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Chinese Physics B 2015年第9期24卷 399-402页

作者：何晓光赵德刚江德生朱建军陈平刘宗顺乐伶聪杨静李晓静张书明杨辉 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences Suzhou Institute of Nano-tech and Nano-bionics Chinese Academy of Sciences

AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas（2DEG） performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the hightemperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 10^13cm^-2, electron mobility of 2101 cm^2·V^-1·s^-1, and square resistance of 249 Ω is obtained.

关键词： high electron mobility transistor two-dimensional electron gas GaN

Tracing the formation of oxygen vacancies at the conductive LaAlO3/SrTiO3 interface via photoemission

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Opto-electronic Science 2022年第7期1卷 33-40页

作者： Junyan Chen Tobias Eul Lu Lyu Yaolong Li Xiaoyong Hu Xingkun Ning Shufang Wang Martin Aeschlimann Qihuang Gong State Key Laboratory for Mesoscopic Physics&Department of Physics Collaborative Innovation Center of Quantum Matter&Frontiers Science Center for Nano-optoelectronicsBeijing Academy of Quantum Information SciencesPeking UniversityBeijing 100871China Department of Physics and Research Center OPTIMAS University of KaiserslauternKaiserslautern 67663Germany College of Physics Science&Technology Hebei UniversityBaoding 071002China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

The two-dimensional electron gas(2DEG)generated at the LaAlO3/SrTiO3 interface has been in the focus of oxides re-search since its first *** oxygen vacancies play an important role in the generation of the insulator-to-metal transition of the SrTiO3 bare surface,their contribution at the LaAlO3/SrTiO3 interface remains *** this work,we investigated a LaAlO3/SrTiO3 heterostructure with regional distribution of defect-based localized polar sites at the *** static and time-resolved threshold photoemission electron microscopy,we prove that oxygen vacan-cies are induced near those polar sites,resulting in the increase of carrier density of the 2DEG *** addition,oxy-gen-related surface states were uncovered,which we attributed to the release of lattice oxygen during the formation of oxygen *** effects are mainly found spatially located around the defect sites at the buried interface,while other regions remain *** results confirm that the itinerant electrons induced by oxygen vacancies can coex-ist with the charge transfer mechanism in the LaAlO3/SrTiO3 heterostructure,together leading to the formation of the metallic *** observations provide fundamental insights into the nature of LaAlO3/SrTiO3 interface based 2DEG and unique perspectives for potential applications.

关键词： two-dimensional electron gas photoemission electron microscopy strontium titanate defect states

Spin relaxation induced by interfacial effects in GaN/Al_(0.25) Ga_(0.75) N heterostructures

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Fundamental Research 2021年第6期1卷 656-660页

作者： Shixiong Zhang Ning Tang Xiaoyue Zhang Xingchen Liu Lei Fu Yunfan Zhang Teng Fan Zhenhao Sun Fentao Wang Weikun Ge Bo Shen State Key Laboratory of Artificial Microstructure and Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Frontiers Science Center for Nano-optoelectronics and Collaboration Innovation Center of Quantum Matter Peking UniversityBeijing 100871China Peking University Yangtze Delta Institute of Optoelectronics Nantong 226010China

Spin relaxation induced by the interfacial effects in GaN/Al_(0.25) Ga_(0.75) N heterostructures was carefully investigated using a photon-energy-dependent time-resolved Kerr rotation *** existence of the interfacial localized states with potential fluctuations at the GaN/AlGaN heterointerface leads to photoluminescence peaks showing blue and S-shaped shifts owing to the excitation power and temperature,*** electrons in the localized states show a spin relaxation time longer than 1 ns because of the suppression of the D’yakonov-Perel’(DP)scattering,while the spin relaxation time of free electrons was approximately only 10 ps because of the giant Rashba spin-orbit coupling induced by the interfacial polarization field under the framework of the DP scattering ***,it is found that the high electron mobility at the heterointerface results in a long spin diffusion length of 300 nm at high temperatures,which is promising for the development of GaN-based spintronic devices.

关键词： GaN/AlGaN heterointerface two-dimensional electron gas Interfacial localized state Spin dynamics Polarization field

Self-consistent analysis of double-δ- doped InA1As/InGaAs/InP HEMTs

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Chinese Physics B 2006年第11期15卷 2735-2741页

作者：李东临曾一平 Novel Materials Laboratory Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China

We have carried out a theoretical study of double-5-doped InAlAs/InGaAs/InP high electron mobility transistor （HEMT） by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas （2DEG） and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be 5 × 10^12 and 3× 10^12 cm^-2 for the upper and lower impurity layers, respectively, in the double-5-doped InAlAs/InGaAs/InP HEMTs.

关键词： two-dimensional electron gas high electron mobility transistor self-consistent calculation,InAlAs/InGaAs heterostructure