Analysis of the Photoluminescence Spectra of Heterostructures with AlGaAs/GaAs Quantum Wells

Journal of Communications Technology and Electronics - A technique for the examination of the photoluminescence spectra of multilayer heteroepitaxial structures with AlGaAs/GaAs quantum wells grown...     

Self-Consistent Simulation of GaAs/InGaAs/AlGaAs Heterostructures Photoluminescence Spectra and Its Application to pHEMT Structures Diagnostics

We performed numerical self-consistent solution of Schrödinger and Poisson equations for GaAs/InGaAs/AlGaAs pHEMT structures with quantum well. Based on the results we calculated optical transition matrix elements and photoluminescence spectra of such structures with the same design and different parameters (such as doping level and epitaxial layers width). In the photoluminescence spectra calculations three fitting parameters have been used. These parameters are GaAs/InGaAs valence band offset in strained quantum well, hole quasi Fermi level and inhomogeneous broadening. The PL peaks amplitudes and positions dependencies on the structure parameters were established. These dependencies can be used as the basis for pHEMT structure non-destructive diagnostics.     

Injection-Current Dependence of the Acoustoelectric Signal in AlGaAs/GaAs Heterostructures

Acoustic charge transport is studied experimentally and theoretically. To this end, an AlGaAs/GaAs heterostructure is designed and fabricated with set geometrical and electrical parameters of the layers. Its transfer characteristic is measured, i.e., the variation of output voltage with injection current. The behavior of the curve is explained within an analytical model. The conclusions are supported by numerical simulation.     

Thermopower of a 2D Electron Gas in Suspended AlGaAs/GaAs Heterostructures

We present thermopower measurements on a high electron mobility two-dimensional electron gas (2DEG) in a thin suspended membrane. We show that the small dimension of the membrane substantially reduces the thermal conductivity compared with bulk material so that it is possible to establish a strong thermal gradient along the 2DEG even over a distance of a few micrometers. We find that the zero-field thermopower is significantly affected by the micropatterning. In contrast to 2DEGs incorporated in a bulk material, the diffusion contribution to the thermopower remains dominant up to temperature of 7?K, until the phonon drag becomes strong and governs the thermopower. We also find that the coupling between electrons and phonons in the phonon-drag regime is due to screened deformation potentials, in contrast to the piezoelectric coupling found for bulk phonons.     

Dopant Migration-Induced Interface Dipole Effect in n-Doped GaAs/AlGaAs Terahertz Detectors

A heterojunction interfacial workfunction internal photoemission (HEIWIP) terahertz detector with ~1times10¹⁸cm^-3 n-type doped GaAs emitters in a multilayer GaAs/Al_0.13Ga_0.87 As heterostructure is presented. The detection mechanism is based on free carrier absorption with a broad response extending to ~ 5.26 THz (57 mum), corresponding to an effective workfunction of ~ 21.8 meV, which is much smaller than the offset expected for an Al fraction of x = 0.13 at a 1times10¹⁸ cm^-3 doping. This is attributed to a reduction of the conduction band offset by interface dipole formation between the accumulated negative charges at the interface states and migrated positively charged donors in the barrier. The device has a peak responsivity of 0.32 A/W at ~ 26 mum at 5 K. It is demonstrated that the dopant migration-induced interface dipole effect can be used to extend the zero response threshold frequency (f ₀) of n-type HEIWIP detectors.     

GaAs/AlGaAs多量子阱结构的光吸收谱和横向光电流谱

研究了MBE GaAs/AlGaAs多量子阱结构的横向光电流谱和光吸收谱。在光电流谱中观测到多种允许和禁戒的激子吸收峰以及一个阱中受主态至n=1电子态的非本征吸收峰。确定出5个空穴子带至2个电子子带的跃迁以及这些子带的间距。采用简单带方势阱模型并取参数Q_c=0.6,m_c=0.0665,m_h=0.45和m_l=0.12的计算结果与实验数据符合得相当好。将光吸收谱与光荧光谱进行了比较。     

GaAs/AlGaAs梯度折射率分别限制单量子阱结构中的光增益谱分析

对不同阱宽的梯度折射率分别限制单量子阱激光器进行了TE、TM模的光增益谱测量对于阱宽大于120A的激光器,发射光谱和光增益谱都出现双峰,分别是由n=1和n=2的子带跃迁所造成,激光振荡出现在n=2的子带跃迁。随着阱宽减小,n=1子带跃迁的饱和增益增加,使激光振荡能在n=1子带发生,而n=2子带的受激就需要比原来更大的注入才有可能。材料增益随阱宽减小呈超线性地增加,从而降低了n=1子带受激的最小腔长。因此,用较窄的量子阱(≤100A),高的端面反射率和尽可能短的腔长,就能得到很低的阈电流。TE和TM模增益谱的不同,使激光器在一定阱宽和腔损耗下具有不同的TE和TM激射波长。     

Generation of Terahertz Radiation Spectra by Radiation Sources Based on Solid-State Micro- and Nanostructures and Detection of Terahertz Spectra

Principles and mechanisms of generation of terahertz electromagnetic oscillations by generators based on solid-state micro- and nanostructures are discussed. Parameters of experimental models of such devices are given. A theoretical model of terahertz radiation in magnetic metal junctions is presented, and the possibility of varying the frequency of a spin-injection terahertz oscillator is demonstrated. The results of development of methods for examining the spectral characteristics of radiation in the 0.15–80 THz range with a spectral resolution of up to 1.8 GHz are detailed.     

Features of Creating Ohmic Contacts for GaAs/AlGaAs Heterostructures with a Two-Dimensional Electron Gas

The literature concerning the features of creating ohmic contacts for GaAs/AlGaAs heterostructures with a two-dimensional (2D) electron gas with a high level of electron mobility is analyzed. The process of annealing the contacts based on the Ni/Au/Ge system is considered. The recommended published parameters of the layers to be sprayed and the regimes of their annealing are presented, which make it possible to obtain ohmic contacts with low resistance up to temperatures lower than 4 K. Several mechanisms are considered, which can lead to the experimentally observed dependence of the characteristics of the contact on its crystallographic orientation. A method for creating contacts using Au/Ge/Pd metallization, in which the contact is formed due to the mutual diffusion and interaction of metals and a semiconductor in the solid phase at temperatures lower than 200°C, is described. This ensures a higher degree of homogeneity of the contact in the composition and a smooth metal–semiconductor interface, and it can lead to decrease of the influence of orientation effects on the electric characteristics of the contact.     

Terahertz electroluminescence originating from spatially indirect intersubband transitions in a GaAs/AlGaAs quantum-cascade structure

The terahertz electroluminescence of a GaAs/AlGaAs quantum-cascade structure in the range ～33–60 cm^?1 (1–1.8 THz) is studied and an energy-level diagram of the structure is calculated. The strongest transitions in this system are analyzed and their dependence on the applied electric field is investigated. The analysis indicates that the observed line of terahertz radiation can be related to spatially indirect transitions of electrons between the states localized in neighboring quantum wells and corresponding to the minima in the quantum-confinement subbands. The results of numerical simulations satisfactorily describe the spectral position of the electroluminescence line and its shift as the bias voltage increases across the quantum-cascade structure.     

低温生长砷化镓光电导天线产生太赫兹波的辐射特性

研究了低温生长砷化镓光电导天线(LT-GaAs PCA)产生太赫兹(THz)波的辐射特性。利用太赫兹时域光谱(TDS)技术测量了光电导发射极在飞秒激光作用下辐射的太赫兹脉冲,得到了时域发射光谱,并通过快速傅里叶变换(FFT)得到相应的频域光谱。结果表明,低温砷化镓光电导天线产生的太赫兹波信号比飞秒激光激发半导体表面产生的太赫兹波信号具有更高的强度和信噪比;太赫兹波信号与光电导天线的偏置电压成线性关系;随着抽运激光功率的增强,太赫兹波信号增大并出现饱和。     

Switching Control Model of Closed-Mode Structures in Large Rectangular Cavities Based on AlGaAs/InGaAs/GaAs Laser Heterostructures

Semiconductors - A lumped model of the dynamics of the controlled switching of high-Q closed-mode structures in rectangular large cavities (up to 1 × 1 mm and larger) based on...     

Analysis of a resonant-cavity enhanced GaAs/AlGaAs MSMphotodetector

The authors have developed a 2-D device simulator for heterostructure metal-semiconductor-metal (MSM) photodetectors. They have incorporated a model of multilayer optics into the simulator and used it to analyze the temporal response of a resonant-cavity enhanced heterostructure with a confining buffer layer and a distributed Bragg reflector (DBR). The authors show that through fine tuning the layer thicknesses, optical resonance enhancement of the light absorption can be obtained     

Electron mobility in a AlGaAs/GaAs/AlGaAs quantum well

An oscillatory dependence of the electron mobility on the quantum well (QW) thickness in a AlGaAs/GaAs/AlGaAs heterostructure with double-sided modulation doping has been observed experimentally. A steep decrease in mobility with increasing electron concentration in the QW is established. The conditions for an increase in mobility on introducing a thin barrier into the QW are determined. The first experimental observation of an increase in mobility by a factor of 1.3 in a QW of thickness L=26 nm upon introducing a thin (1–1.5 nm) AlAs barrier is reported.     

Ultra-submicrometer-gate AlGaAs/GaAs HEMTs

Ultra-submicrometer-gate AlGaAs/GaAs high-electron-mobility transistors (HEMTs) that have gate lengths ranging from 25 to 85 nm and were fabricated using electron-beam lithographic techniques on epitaxial wafers grown by molecular beam epitaxy are discussed. These devices show that velocity overshoot and short-gate geometry effects play an important role for the gate lengths less than 100 nm. The maximum intrinsic transconductance is 215 mS/mm, and the effective saturated electron velocity reaches 3×10⁷ cm/s for a 30-nm HEMT     

单量子阱GaAs/AlGaAs半导体激光器

本文介绍了用分子束外延法制作的梯度折射率分别限制式单量子阱GaAs/AlGaAs半导体激光器。该器件具有较低的阈值电流密度和单模运转特性,连续输出功率可达55mw。     

AlGaAs/GaAs/AlGaAs DHBT's for high-temperature stable circuits

High-temperature devices are required for a large number of industrial applications. In order to demonstrate the feasibility of a high temperature operating circuit on GaAs an operational amplifier was designed and fabricated. A corresponding technology for transistors and circuits for operation up to 300°C with AlGaAs/GaAs/AlGaAs DHBT's is presented. For the amplifier circuit an open loop gain of 49.5 dB at room temperature and 35.8 dB at 200°C was measured, which is in good agreement with the circuit simulation. High temperature stability has been proven by a storage test at 400°C over 1000 h for the ohmic contact metallization and 200 h for the transistors