Extrinsic Base Surface Passivation in High Speed ＂Type-II＂ GaAsSb/InP DHBTs Using an InGaAsP Ledge Structure

有有选择地蚀刻的 InGaAsP 壁结构的 Type-II GaAsSb/InP DHBT 第一次被制作并且描绘。有 20 nm 的新奇 InGaAsP/GaAsSb/InP DHBT 匹配格子的 GaAsSb 底和 75 nm InP 收集者由 2 的一个因素和 190 GHz 的截止频率英尺有 dc 电流获得改进。InGaAsP 壁设计提供一条简单却有效的途径压制外来的基础表面再结合并且使 GaAsSb/InP DHBT 能进一步为毫米波浪应用增加操作频率和集成层次。[从作者抽象]

Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.

Gate-Recessed AlGaN/GaN MOSHEMTs with the Maximum Oscillation Frequency Exceeding 120 GHz on Sapphire Substrates

Gate-recessed AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) on sapphire substrates are fabricated.The devices with a gate length of 160nm and a gate periphery of 2 × 75μmexhibit two orders of magnitude reduction in gate leakage current and enhanced off-state breakdown characteristics,compared with conventional HEMTs.Furthermore,the extrinsic transconductance of an MOSHEMT is 237.2mS/mm,only 7% lower than that of Schottky-gate HEMT.An extrinsic current gain cutoff frequency fT of 65 GHz and a maximum oscillation frequency fmax of 123 GHz are deduced from rf small signal measurements.The high fmax demonstrates that gate-recessed MOSHEMTs are of great potential in millimeter wave frequencies.

Optimization of ohmic contact for InP-based transferred electronic devices

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.210 7 cm2was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 ℃. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 51018cm 3in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 ℃.

A 20-GHz ultra-high-speed InP DHBT comparator

An ultra-high-speed, master-slave voltage comparator circuit is designed and fabricated using InP/GaInAs double heterojunction bipolar transistor technology with a current gain cutoff frequency of 170 GHz. The complete chip die, including bondpads, is 0.75 × 1.04 mm22. It consumes 440 mW from a single M V power supply, excluding the clock part. 77 DHBTs have been used in the monolithic comparator. A full Nyquist test has been performed up to 20 GHz, with the input sensitivity varying from 6 mV at l0 GHz to 16 mV at 20 GHz. To our knowledge, this is the first InP based integrated circuit including more than 70 DHBTs, and it achieves the highest sampling rate found on the mainland of China.

蓝宝石衬底上NaOH辅助CVD法制备有序单层MoS2条带

本文报道了一种在蓝宝石衬底上NaOH辅助化学气相沉积(CVD)生长有序排列单层MoS2条带的方法.MoS2条带具有优良的单晶性,其载流子迁移率为~150 cm^2V^-1s^-1,在550 nm波长下的光学响应为103 mA W^-1.单层MoS2条带在蓝宝石衬底上具有两种生长方式,其中一种为受层间范德华力以及晶格影响的取向生长,另一种为受蓝宝石台阶约束的平行生长.NaOH的引入量对MoS2形态与取向起重要作用,可以实现从取向性三角形晶畴,受衬底晶格影响的取向MoS2条带,受衬底台阶约束的平行条带,再到大尺寸杂乱取向三角形晶畴的连续可调.本文的结果有利于推动MoS2的基础研究及器件应用,也为合成其他一维和二维纳米结构开辟了新途径.

A Verilog-A large signal model for InP DHBT including thermal effects

A large signal model for InP/InGaAs double heterojunction bipolar transistors including thermal effects has been reported,which demonstrated good agreements of simulations with measurements.On the basis of the previous model in which the double heterojunction effect,current blocking effect and high current effect in current expression are considered,the effect of bandgap narrowing with temperature has been considered in transport current while a formula for model parameters as a function of temperature has been developed.This model is implemented by Verilog-A and embedded in ADS.The proposed model is verified with DC and large signal measurements.

通过亚甲基蓝表面修饰实现对生长在铂上的石墨烯的无损可视化

对石墨烯质量的高效大规模的无损检测是推进其生长研究和实际应用的关键.在这里,我们报告了一种非常简单的方法:用普通的光学显微镜来直接观测生长在铂上的石墨烯的形貌和缺陷.该工艺通过亚甲基蓝(MB)对在铂上的石墨烯进行修饰来实现.由于石墨烯和铂表面的化学活性不同,MB在石墨烯和铂表面的吸附和反应也不同.通过对比光学图像中的颜色,我们可以观测到石墨烯晶畴和缺陷的分布.此外,该表征方法对铂衬底和石墨烯均无明显损伤,不影响衬底的再利用和石墨烯的后续表征或应用.我们的工作为大规模检测生长在铂上的石墨烯的质量提供了一种非破坏性的方法,也为其他检测二维材料的质量和掺杂情况提供了参考.