Photodiffraction in InGaAs/InGaAsP multiple quantum wells enclosed in a microcavity

We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm⁻², and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation.     

长波长大应变InGaAs/InGaAsP分布反馈激光器的材料生长与器件制备

采用低压金属有机化合物气相沉积法(LP-MOCVD)生长并制作了1.6—1.7μm大应变InGaAs/InGaAsP分布反馈激光器.采用应变缓冲层技术，得到质量良好的大应变InGaAs/InP体材料.器件采用了4个大应变的量子阱，加入了载流子阻挡层改善器件的温度特性.1.66μm和1.74μm未镀膜的3μm脊型波导器件阈值电流低(小于15mA)，输出功率高(100mA时大于14mW).从10—40℃，1.74μm激光器的特征温度T₀=57K，和1.55μm InGaAsP分布反馈激光器的特征温度相当. 关键词： MOCVD InGaAs/InGaAsP 应变量子阱 分布反馈激光器     

Electron g-factor in a gated InAs-inserted-channel In0.53Ga0.47As/In0.52Al0.48As heterostructure

We report on electron g-factor in an InAs-inserted In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructure. The gate voltage dependence of g-factor is obtained from the coincidence method. The obtained g-factor values are surprisingly smaller than the g-factor value of bulk InAs, and it is close to the bare g-factor value of In_0.53Ga_0.47As. The large change in g-factor is observed by applying the gate voltage. The obtained gate voltage dependence is not simply explained by the energy dependence of g-factor.     

Enhanced Static Modulated Fourier Transform Spectrometer for Fast Approximation in Field Application

We discuss the data sampling frequency, the spectral resolution, and the limit for non-aliasing in the static modulated Fourier transform spectrometer based on a modified Sagnac interferometer. The measurement was performed in a very short 4 ms, which is applicable for real time field operation. The improved spectrometer characteristics were used to investigate the spectral properties of an InGaAs light emitting diode. In addition, The measured spectral peak was shifted from 6420 cm⁻¹ to 6365 cm⁻¹, as the temperature increased from 25 °C to 40 °C, when the operating current is fixed to be 0.55 A. As the applied current increased from 0.30 A to 0.55 A at room temperature, the spectral width was broadened from 316 cm⁻¹ to 384 cm⁻¹. Compared to the conventional Fourier transform spectrometer, the measured spectral width by the static modulated Fourier transform spectrometer showed a deviation less than 10%, and the spectral peak shift according to the temperature rise showed a difference within 2%.     

Investigation of the electrical and optical properties of InAs/InGaAs dot in a well solar cell

The electroreflectance (ER) and current–voltage (J–V) of InAs/InGaAs dots in a well (DWELL) solar cell (SC) were measured to examine the optical and electrical properties. To investigate the carrier capturing and escaping effects in the quantum dot (QD) states the above and below optical biases of the GaAs band gap were used. In the reverse bias region of the J–V curve, the tunneling effect in the QD states was observed at low temperature. The ideality factors (n) were calculated from the J–V curves taken from various optical bias intensities (I_ex). The changes in the ideality factor (n) and short circuit current (J_SC) were attributed mainly to carrier capture at low temperature, whereas the carrier escaping effect was dominant at room temperature. ER measurements revealed a decrease in the junction electric field (F_J) due to the photovoltaic effect, which was independent of the optical bias source at the same temperature. At low temperature, the reduction of photovoltaic effect could be explained by the enhancement carrier capturing effect due to the strong carrier confinement in QDs.     

基于线阵InGaAs光电二极管阵列的光纤光栅传感解调

采用线阵InGaAs光电二极管阵列和体相位光栅并结合空分复用和波分复用技术,对光纤光栅传感进行解调.设计了基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅传感解调系统,通过系统测试和性能分析,该解调系统解调带宽42 nm,信噪比30 dB,波长偏移测量精确度±15 pm,功率测量精确度为±0.3 dB.基于线阵InGaAs光电二极管阵列和体相位光栅的光纤光栅解调系统不但尺寸小,功耗低,而且具有较高的解调速度.     

III–V quantum devices and circuits based on nanoscale Schottky gate control of hexagonal quantum wire networks

The concept, the present status, key issues and future prospects of a novel hexagonal binary decision diagram (BDD) quantum circuit approach for III–V quantum large-scale integrated circuits (QLSIs) are presented and discussed. In this approach, the BDD logic circuits are implemented on III–V semiconductor-based hexagonal nanowire networks controlled by nanoscale Schottky gates. The hexagonal BDD QLSIs can operate at delay-power products near the quantum limit in the quantum regime as well as in the many-electron classical regime. To demonstrate the feasibility of the present approach, GaAs Schottky wrap gate (WPG)-based single-electron BDD node devices and their integrated circuits were fabricated and their proper operations were confirmed. Selectively grown InGaAs sub-10 nm quantum wires and their hexagonal networks have been investigated to form high-density hexagonal BDD QLSIs operating in the quantum regime at room temperature.     

Molecular dynamics simulation comparison of atomic scale intermixing at the amorphous Al2O3/semiconductor interface for a-Al2O3/Ge, a-Al2O3/InGaAs, and a-Al2O3/InAlAs/InGaAs

The structural properties of a-Al₂O₃/Ge, a-Al₂O₃/In_0.5Ga_0.5As and a-Al₂O₃/In_0.5Al_0.5As/InGaAs interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic a-Al₂O₃ samples were generated using a hybrid classical-DFT MD “melt and quench” approach. The interfaces were formed by annealing at 700 K/800 K and 1100 K with subsequent cooling and relaxation. The a-Al₂O₃/Ge interface demonstrates pronounced interface intermixing and interface bonding exclusively through Al–O–Ge bonds generating high interface polarity. In contrast, the a-Al₂O₃/InGaAs interface has no intermixing, Al–As and O–In/Ga bonding, low interface polarity due to nearly compensating interface dipoles, and low substrate deformation. The a-Al₂O₃/InAlAs interface demonstrated mild intermixing with some substrate Al atoms being adsorbed into the oxide, mixed Al–As/O and O–Al/In bonding, medium interface polarity, and medium substrate deformation. The simulated results demonstrate strong correlation to experimental measurements and illustrate the role of weak bonding in generating an unpinned interface for metal oxide/semiconductor interfaces.     

具有InAlAs浸润层的InGaAs量子点的制备和特性研究

采用自组装方法生长了一种新型的InGaAs量子点/InAlAs浸润层结构.通过选取合适的In组分 ，使InAlAs浸润层的能级与GaAs势垒相当，从而使浸润层的量子阱特征消失.通过低温光致 发光（PL）谱的测试分析得到InGaAs量子点/InAlAs浸润层在样品中的确切位置.变温PL谱的 研究显示，具有这种结构的量子点发光峰的半高全宽随温度上升出现展宽，这明显区别于普 通InGaAs量子点半高全宽变窄的行为.这是因为采用了InAlAs浸润层后，不仅增强了对InGaA s量子点的限制作用，同时切断了载流子的 关键词： InGaAs量子点 InAlAs浸润层 PL谱     

Single-electron transistor spectroscopy of InGaAs self-assembled quantum dots

A single-electron transistor (SET) is used to detect tunneling of single electrons into individual InGaAs self-assembled quantum dots (QDs). By using an SET with a small island area and growing QDs with a low density we are able to distinguish and measure three QDs. The bias voltage at which resonant tunneling into the dots occurs can be shifted using a surface gate electrode. From the applied voltages at which we observe electrons tunneling, we are able to measure the electron addition energies of three QDs.