808 nm大功率半导体激光器阵列的优化设计

 采用激射波长为808 nm的GaAs/AlGaAs梯度折射率波导分别限制单量子阱结构外延片,制备了沟道深度不同的半导体激光器阵列,并对载流子分布进行理论分析和模拟。理论和实验结果表明：引入脊形台面和隔离沟道后,激光器阵列的输出功率、电光转换效率、斜率效率和光谱特性均有显著提高。随着沟道的加深,对电流侧向扩散的限制作用增强,从而提高了阵列性能。     

High power-added-efficiency AlGaN/GaN HEMTs fabricated by atomic level controlled etching

An atomic-level controlled etching(ACE)technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors(HEMTs)with high power added efficiency.We compare the recessed gate HEMTs with conventional etching(CE)based chlorine,Cl₂-only ACE and BCl³/Cl₂ACE,respectively.The mixed radicals of BCl₃/Cl₂were used as the active reactants in the step of chemical modification.For ensuring precise and controllable etching depth and low etching damage,the kinetic energy of argon ions was accurately controlled.These argon ions were used precisely to remove the chemical modified surface atomic layer.Compared to the HEMTs with CE,the characteristics of devices fabricated by ACE are significantly improved,which benefits from significant reduction of etching damage.For BCl₃/Cl₂ACE recessed HEMTs,the load pull test at 17 GHz shows a high power added efficiency(PAE)of 59.8%with an output power density of 1.6 W/mm at Vd=10 V,and a peak PAE of 44.8%with an output power density of 3.2 W/mm at Vd=20 V in a continuous-wave mode.     

A statistical model for the effect of casing treatment recesses on compressor rotor performance

The tip clearance between a compressor’s rotating blades and its casing has an unfavorable influence on performance. By applying an abradable coating (insert) to the casing over the rotating blades, this tip clearance can be reduced to practically zero. A rather frequent variant is for the rotor blade tips to carve an entire annular recess in this coating. Rectangular recesses of various configurations have been tested in several different researches. The results of these investigations are processed using the Group Method of Data Handling. A statistical model is developed that predicts the influence of rectangular recesses on a compressor stage’s efficiency and stable operating (flow) range. The model takes into account the six principal geometric parameters of a rectangular recess, as well as the Lieblein rotor diffusion factor. Analysis of the derived model has also determined which of these parameters are the most influential. Rectangular entire annular recesses are one of the simplest and most progressive types of casing treatment, and this paper concludes with an overview of existing research that supports this claim.     

Impact of gate offset in gate recess on DC and RF performance of InAlAs/InGaAs InP-based HEMTs

A set of 100-nm gate-length InP-based high electron mobility transistors (HEMTs) were designed and fabricated with different gate offsets in gate recess. A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography. DC and RF measurement was conducted. With the gate offset varying from drain side to source side, the maximum drain current (I_ds,max) and transconductance (g_m,max) increased. In the meantime, f_T decreased while f_max increased, and the highest f_max of 1096 GHz was obtained. It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance. Output conductance was also suppressed by gate offset toward source side. This provides simple and flexible device parameter selection for HEMTs of different usages.