Influence of oxygen in AlGaAs-based laser structures with Al-Free active region on device properties

AlGaAs-based lasers with GaAsP active regions for emission wavelengths near 730 nm and 800 nm were studied. Trimethyl aluminum sources with different levels of oxygen concentration were used for the deposition of the laser structures. The laser data show that the oxygen level in the AlGaAs wave guides is very critical for the performance of the 730 nm devices, even for the use of an Al-free active region, while its influence is weak for the 800 nm devices. Using the TMAl source leading to the lowest O-uptake in the AlGaAs wave guides from such structures, 7 W output power and a degradation rate of 1 10⁻⁵h⁻¹ at 2 W cw (100 μm stripe width × 4 mm, 25°C, 2000 h) are achieved for 730 nm emission.     

静压下GaAs_(1-x)P_x混晶的喇曼散射

在77K下和0—60kbar静压范围内测量了GaAs_(1-x)P_x(0.76 ≤x≤1)混晶的喇曼散射谱。得到了这些混晶的类GaP的LO模的压力系数。发现在所研究的x范围内GaAs_(1-x)P_x混晶的类GaP的LO模的压力行为与Gap的LO模基本相同。利用测得的压力系数计算了类GaP的LO模的模式Gruneisen参数。     

Thin layers of GaInP, GaP and GaAsP in metalorganic vapour phase epitaxy-grown resonant tunnelling diodes

We have studied the epitaxial growth and electrical performance of Al-free, GaAs-based, resonant tunnelling diodes (RTDs) including thin barriers of GaInP, GaP, or GaAs_xP_1−x. n-Type tunnelling diodes have been fabricated and the symmetry in the current–voltage (I–V) characteristics, as well as the peak-to-valley ratios, are found to be sensitive probes for the interface quality in the heterostructures. For GaInP RTDs, we show that the introduction of GaP intermediate layers is crucial for the realisation of a useful tunnelling current. RTDs including thin barriers (less than about 10 monolayers (ML)) of GaP are realised, but the strong mismatch between the materials limit the useful thickness. Finally, RTDs with GaAs_xP_1−x alloys are fabricated showing the best peak-to-valley ratio of the diodes (about 5), as well as a symmetric I–V characteristics. The electrical data are further compared to studies by transmission electron microscopy (TEM) in the various material systems.     

Magnetic properties of donors in GaAsP

The magnetic properties of hydrogenic Te donors and bistable,DX-like S donors in GaAS _x P_1-x have been investigated. Te shows an EPR signal after cooling down, both in the dark. The EPR signal from S appears only after illumination. S does not show an EPR signal after cooling down in the dark, but after illumination when the hydrogenic state of this donor is populated. Static magnetic susceptibility measurements show however that the ground state of S in GaAs _x P_1-x is paramagnetic even though it does not produce an EPR signal. This is in agreement with a one-electron ground state of this bistable donor.     

A study of estimation method for conduction band offset in semiconductor heterostructure by using triple-barrier resonant tunneling diodes

A method for evaluating a band offset of a heterojunction is proposed by measuring temperature dependence of current–voltage (I–V) characteristics in triple-barrier resonant tunneling diodes (TBRTDs). The method was applied for investigating a conduction band offset by using GaAs_0.25P_0.75/GaAs TBRTDs with thin strain heterobarriers grown by MOCVD and ΔE_c was estimated as 200–240 meV. In the strain-barrier TBRTDs, negative differential resistance was observed below 100 K.     

60%电光效率高功率激光二极管阵列

设计并制备了980 nm高量子效率和极低光损耗的激光二极管(LD)外延材料和器件.微通道封装1 cm激光二极管阵列在连续(CW)工作条件下最大电光效率达到60.0%,相应的斜率效率和输出光功率分别为1.1W /A和38.2 W.测试得到外延材料的内损耗系数和内量子效率分别为0.58 cm-1和91.6%.测试分析表明,器件电光效率的提高主要在于新型的InGaAs/GaAsP应变补偿量子阱和大光腔结构设计.     

808 nm大功率无铝有源区非对称波导结构激光器

采用分别限制非对称波导结构,将光场从对称分布变为非对称分布,降低了载流子光吸收损耗,并允许p型区具有更高的掺杂水平,从而使器件电阻降低.对GaAsP/GaInP张应变单量子阱(SQW)非对称波导结构激光器的光场特性进行了理论分析,设计了波导层厚度,并制作了波长为808 nm的无铝有源区大功率半导体激光器.器件综合特性测试结果为:腔长900μm器件的阈值电流密度典型值为400 A/cm2,内损耗低至1.0 cm-1;连续工作条件下,150μm条宽器件输出功率达到6 W,最大斜率效率为1.25 W/A.器件激射波长为807.5 nm,平行和垂直结的发散角分别为3.0°和34.8°.20~70℃范围内特征温度达到133 K.结果表明,分别限制非对称波导结构是降低内损耗,提高大功率半导体激光器特性的有效措施.     

Characterization of the iron and nickel impurities in gaas0.6p0.4

Characterization of nickel and iron impurity centers in GaAs_0.6P_0.4 has been made using the technique of capacitance transients on reverse biased zinc-diffused p⁺n diodes. Both the nickel and iron levels have been identified by thermal hole emission having activation energies of 0.3eV and 0.58eV, respectively. Relative photoresponse measurements resulted in a threshold for optical hole emission of 0.3eV and 0.58eV, therefore, confirming the thermal hole emission measurements. Capture studies for nickel and iron centers indicated a relatively large capture cross-section and a strong electric field dependence. This work is supported by the National Science Foundation, Grant ENG76-80128.     

Growth of GaInP/GaAsP short period superlattices by flow modulation organometallic vapor phase epitaxy

One disadvantage of the GalnP/GaAs system is the difficulty often encountered in synthesizing the quaternary material GalnAsP, required to span the intermediate bandgap range (1.42–1.91 eV). Recent studies report on an extensive miscibility gap in this alloy. In this study, we investigate an alternative approach to the growth of material within this bandgap range. We have grown by flow-modulation organometallic vapor phase epitaxy, GalnP/GaAsP superlattices with periods ranging from 80 to 21Å. These are the first reported short-period superlattices in this material system. Effects of superlattice (SL) period, growth temperature, and phosphorous composition in the wells were studied by photoluminescence, high resolution x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The effect of growth temperature on the structural quality of the SLs is correlated to ordering effects in the GalnP layers. Variations in the P composition and the SL period result in a shift in the room temperature bandgap emission from 1.51 to 1.74 eV. Strain-compensated structures have been realized by growing the SL barriers in compression.     

Phosphorus incorporation in GaAsP grown by remote-plasma MOCVD

Epitaxial layers of GaAs and GaAs_xP_1−x were deposited under a variety of conditions using a remote plasma in a metal-organic chemical vapor deposition (MOCVD) reactor. The remote rf plasma dissociated AsH₃ and PH₃ into highly reactive radicals increasing the growth rate at low temperatures and increasing the phosphorus incorporation at temperatures below 850° C. GaAs_xP_1−x with a high P content could be grown at low deposition temperatures by using the plasma to increase the reactivity of PH₃. The growth rate of both GaAs and GaAs_xP_1−x was increased at low temperatures and GaAs_xP_1−x was grown at temperatures down to 550° C.