Influence of spacer layer thickness on the current-voltage characteristics of pseudomorphic AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes

This paper investigates the dependence of current voltage characteristics of AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes （RTDs） on spacer layer thickness. It finds that the peak and the valley current density J in the negative differential resistance （NDR） region depends strongly on the thickness of the spacer layer. The measured peak to valley current ratio of RTDs studied here is shown to improve while the current density through RTDs decreases with increasing spacer layer thickness below a critical value.     

生长在p-GaAs衬底上的ZnO基异质结二极管电致发光

利用等离子体辅助分子束外延在p型砷化镓衬底上制备了ZnO异质结发光二极管。实验表明:GaAs与ZnO之间的氧化镁绝缘层能够有效改善器件光电性能,I-V特性的研究表明该器件具有良好的整流特性,开启电压为3V,电致发光光谱由一个紫外发光峰和一个可见发光带构成,其来源分别为ZnO层中近带边缺陷以及深能级缺陷相关的辐射复合。     

半导体量子器件物理讲座第四讲 共振隧穿器件及其电路应用

当一个电子的能量低于势垒高度时,它仍可以隧穿通过势垒,在一定条件下,双势垒结构中电子的隧穿几率甚至可以接近1,利用这种共振隧穿现象可以做成共振隧穿二极管,它的电流－电压特性曲线中会出现负微分电阻,利用这种负阻效应可以做成高频振荡器和倍频器等电子器件,双势垒结构与通常的双极晶体管结合可以做成共振隧穿双极晶体管,它们可以用来做成多态记忆器和模数转换器等器件。     

Nanoelectronic devices---resonant tunnelling diodes grown on InP substrates by molecular beam epitaxy with peak to valley current ratio of 17 at room temperature

This paper reports that InAs/In$_{0.53}$Ga$_{0.47}$As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm$^{2}$ has been obtained for diodes with AlAs barriers of ten monolayers, and an In$_{0.53}$Ga$_{0.47}$As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.     

A bistable, self-latching inverter by the monolithic integration of resonant tunnelling diode and high electron mobility transistor

This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor (HEMT) and AlAs/GaAs resonant tunnelling diode (RTD) are epitaxially grown by molecular beam epitaxy (MBE) in turn on a GaAs substrate. An Al_0.24Ga_0.76As chair barrier layer, which is grown adjacent to the top AlAs barrier, helps to reduce the valley current of RTD. The peak-to-valley current ratio of fabricated RTD is 4.8 and the transconductance for the 1-μm gate HEMT is 125mS/mm. A static inverter which consists of two RTDs and a HEMT is designed and fabricated. Unlike a conventional CMOS inverter, the novel inverter exhibits self-latching property.     

Detection of Fe 3d electronic states in the valence band and magnetic properties of Fe-doped ZnO film

Fe-doped ZnO film has been grown by laser molecular beam epitaxy(L-MBE) and structurally characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM),all of which reveal the high quality of the film.No secondary phase was detected.Resonant photoemission spectroscopy(RPES) with photon energies around the Fe 2p-3d absorption edge is performed to detect the electronic structure in the valence band.A strong resonant effect at a photon energy of 710 eV is observed.Fe3+ is the only valence state of Fe ions in the film and the Fe 3d electronic states are concentrated at binding energies of about 3.8 eV and 7 eV～8 eV.There are no electronic states related to Fe near the Fermi level.Magnetic measurements reveal a typical superparamagnetic property at room temperature.The absence of electronic states related to Fe near the Fermi level and the high quality of the film,with few defects,provide little support to ferromagnetism.     

First resonant tunneling via a light-hole ground state

We report the demonstration of resonant tunneling of light-holes through an AlAs/GaAs P double-barrier heterostructure. The tensile strain in the quantum well reverses the order of the light- and heavy-hole levels, the first light-hole level becoming the ground state. The characteristics are measured at different temperatures and compared to those of a standard AlAs/GaAs unstrained structure. The peak current density of the first light-hole resonance and its peak-to-valley current ratio are enhanced. They reach 28 A/cm and 3.4 : 1 at 15 K. A negative differential resistance is observed up to 250 K.     

GaSb-based type-I quantum well cascade diode lasers emitting at nearly 2-μm wavelength with digitally grown AlGaAsSb gradient layers

We report a GaSb-based type-I quantum well cascade diode laser emitting at nearly 2-μm wavelength. The recycling of carriers is realized by the gradient AlGaAsSb barrier and chirped GaSb/AlSb/InAs electron injector. The growth of quaternary digital alloy with a gradually changed composition by short-period superlattices is introduced in detail in this paper. And the quantum well cascade laser with 100-μm-wide, 2-mm-long ridge generates an about continuous-wave output of 0.8 W at room temperature. The characteristic temperature T₀ is estimated at above 60 K.     

Narrow spectral band monolithic lead-chalcogenide-on-Si mid-IR photodetectors

Narrow spectral band infrared detectors are required for multispectral infrared imaging. Wavelength selectivity can be obtained by placing passive line filters in front of the detectors, or, the preferred choice, by making the detectors themselves wavelength selective. We review the first photovoltaic resonant cavity enhanced detectors (RCED) for the mid-IR range. The lead-chalcogenide (PbEuSe) photodetector is placed as a very thin layer inside an optical cavity. At least one side is terminated with an epitaxial Brugg mirror (consisting of quarter wavelength PbEuSe/BaF₂ pairs), while the second mirror may be a metal. Linewidths are as narrow as 37 nm at a peak wavelength of 4400 nm, and peak quantum efficiencies up to above 50% are obtained. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570B (2005).     

2.0 μm 波段Sb基多量子阱材料的制备

采用分子束外延外延生长技术,优化InGaAsSb/AlGaAsSb多量子阱点材料的生长速率、生长温度和束流比等生长参数,获得了高质量的多量子阱材料。室温光荧光谱表明,材料的发光波长为2.0 m左右。该结果表明,通过优化生长条件和结构参数制备的量子阱材料,可以获得良好的结构质量和光学特性。所制备的器件室温条件下输出功率22 mW,阈值电流300 mA。     

Two crucial factors influencing quality of GaAs on Ge substrate

High-quality GaAs films with fine surfaces and GaAs/Ge interfaces on Ge have been achieved via molecular beam epitaxy. The influence of low temperature annealing and low temperature epitaxy on the quality of the film when GaAs is grown on a （100） 6 ° offcut towards [111] Ge substrate are investigated by analyzing and comparing the GaAs films that are fabricated via three different processes. A low temperature annealing process after high temperature annealing and a low temperature epitaxy process after the initial GaAs growth play a vital role in improving the quality of GaAs film on a Ge substrate.     

GROWTH MODE AND SURFACE RECONSTRUCTION OF GaN(0001) THIN FILMS ON 6H-SiC(0001)

Two-dimensional growth of GaN thin films on an atomically flat C-face 6H-SiC(0001) surface prepared by ultra-high vacuum Si-etching is observed when using an AlN buffer layer in N plasma-assisted molecular beam epitaxy. Scanning tunneling microscopy and reflection high energy electron diffraction observations reveal a series of Ga-stabilized reconstructions which are consistent with those reported for an N-polar GaN(0001) film. The result, including the effect observed previously for GaN thin film on Si-terminated 6H-SiC(0001), agrees with the polarity assignment of heteroepitaxial wurtzite GaN films on polar 6H-SiC substrates, i.e., GaN film grown on SiC(0001) is <0001> oriented (N-face) while that on SiC(0001) is <0001> oriented (Ga-face).     

拓扑绝缘体薄膜和有限尺寸效应

拓扑绝缘体是近年来发现的一类新的量子材料,已成为凝聚态物理的研究热点领域.厚度仅几纳米的拓扑绝缘体薄膜不但具有奇特的物理性质,而且还是拓扑绝缘体应用于平面器件的基础.文章以Bi2Se3为例,介绍了Bi2Se3家族拓扑绝缘体薄膜的分子束外延生长以及其能带、自旋结构和拓扑性质随层厚的演化.这些结果为人工调控拓扑绝缘体的电子结构和物理性质提供了指导.