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.     

高效率GaAsP/AlGaAs张应变量子阱激光二极管

从理论上设计优化了高效率808 nm GaAsP/AlGaAs张应变量子阱激光二极管外延材料的量子阱结构和波导结构参数,并采用低压金属有机气相外延技术实验制备了外延材料.将制作的芯片解理成不同腔长,测试得到外延材料的内损耗系数和内量子效率分别为0.82 cm-1和93.6 %.把腔长为900 μm的单巴条芯片封装在热传...     

高功率VCSEL中应变补偿量子阱的理论设计

利用模型固体理论、k.p理论和Pikus-Bir理论,研究了InGaAs/GaAsP应变补偿量子阱,得出了较为简单通用的设计方法;进而研究了阱宽、InGaAs中In组分和GaAsP中P组分等参数对跃迁波长的影响.理论计算发现,与InGaAs/GaAs普通量子阱相比,InGaAs/GaAsP应变补偿量子阱能提供更深的载流子阱和更大的增益.按照提出的理论设计方法,研制了含InGaAs/GaAsP应变补偿量子阱的垂直腔面发射激光器(VCSEL),理论计算和实验结果相吻合.     

An overview of early studies on persistent photoconductivity and other properties of deep levels in GaAsP: The effect of deep levels on light emitting devices

Laser studies carried out at the University of Illinois in 1966 showed that the shortest wavelength at which lasing could be achieved in GaAsP was dependent on then-type dopant. In particular sulfur doping was found to restrict lasing to longer wavelengths. It was suggested that this could be due to the effect of energy levels associated with the higher conduction band minima. This led in 1967 to an investigation of the effect of Te and S donor levels on the properties of GaAsP near the direct-indirect crossover. Samples throughout the composition range were studied using Hall effect measurements from 55 to 400° K and resistivity measurements under hydrostatic pressure between 0 and 7 kbar at 300, 195, and 77° K. The data on Te-doped samples fit the standard energy band models, but S doping was found to exhibit dramatic persistent photoconductivity and other compositional effects similar to the “DX-center” effects later observed in AlGaAs and other materials. This paper summarizes these results on GaAsP:S, and gives a brief overview of other early investigations in compound semiconductors where energy levels associated with higher lying minima were studied and where, in some cases, nonequilibrium effects were observed. A later study on GaAsP:S is also described which shows the effect of S-doping on LED performance. Finally, some of the implications that the existence of deep levels of this type have on light emitting device performance in other alloy systems is discussed.     

Damage constant and deep-level transient spectroscopy in neutron irradiated GaAsP alloys

Damage produced in VPE GaAs_{1− x P x} . alloys by fast neutron irradiation at room temperature was studied, in light emitting diodes, through the evolution of device carrier lifetime, photoluminescence, electroluminescence and transient capacitance spectroscopy characteristics. Neutron fluxes were in the 10¹³−10¹⁴ neutrons/cm² range so as not to heavily damage the devices. Damage constants are 10⁻⁵ to 10⁻⁶ cm²/s for 0.3 ≤x ≤ 1. The carrier removal rate was ≈; 10 cm⁻¹. Deep-level transient spectroscopy in n-type layers revealed that fast neutrons created a broad center atE _c − 0.7 eV, and at a ≈;1 cm⁻¹ generation rate. For thex ≥ 0.4 composition range studied, trap characteristics and introduction rates were rather independent ofx. From photocapacitance quenching measurements it is suggested that the neutron generated centers are EL2-related.     

The compositional grading of MOCVD-grown GaAs1−xPx via substrate temperature changes

The first application of MOCVD compositional grading by means of substrate temperature changes is reported for the case of GaAs−P_x (0 ≤ x ≤ 0.30). The method is based upon the higher pyrolysis efficiency ratio of AsH₃ relative to PH₃ at lower growth temperatures. The growth upon GaAs substrates commences at a temperature at which this PH₃/ASH₃ thermal cracking efficiency ratio is extremely high; raising the growth temperature decreases this ratio, and hence the As/P ratio in the solid. GaAs_1−xP_x epilayers grown on GaAs by this method display excellent materials properties and are virtually optically and electrically indistinguishable from conventionally-graded epilayers in which the gas phase mole fractions of transport agents are varied at constant temperature. The method is applicable to systems where temperature-dependent cracking efficiency differentials exist.     

Current and efficiency improvement for a GaAsP/SiGe on Si tandem solar cell device achieved by light trapping techniques

A GaAsP/SiGe tandem solar cell on Si substrate has been further fabricated using light trapping techniques, such as texturing and adding a back surface reflector, and thinning the Si substrate. This is of importance to increase the J_sc of the Si_0.18Ge_0.82 bottom cell in this tandem system since bottom cell is current limiting. The J_sc of the bottom cell has been increased by relative 7.4%. This current improvement leads to a predicted efficiency of near 21% for this tandem device, with an absolute efficiency improvement of 0.3% over previous results without light trapping processes. The current of the bottom cell can be further improved by optimizing the bottom cell structure and texturing process, further thinning the Si substrate and increasing Ge concentration. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

GaAsP混晶中Te施主深能级的研究

用深能级瞬态谱(DLTS)方法研究了组分范围为x=0.11-0.95的掺Te的GaAs_(1-x)P_(?)混晶中的深能级.结果表明:样品中出现的深能级可分为A,B,C三类,其发射率激活能各约为:E_(?)~A=0.18ev,E_(?)~B=0.28eV,E_(?)~C=0.38eV.其中只有A能级在x=0.23-0.95间的所有样品中出现,B和C能级的出现不存在明显的规律性.进一步研究了A能级的性质后,认为它来源于Te替位杂质的DX中心,而B、C能级的性质可能比较复杂.     

Influence of arsenic overpressure on Light-Output and degradation behavior of GaAsP: Se Led’s

GaAsP: Se LED’s exhibit low quantum efficiencies if diffused under high arsenic overpressure. A high arsenic pressure during the diffusion process on the other hand results in small rates of initial degradation. If GaAsP: Se LED’s are annealed at 600° C under arsenic overpressure their light-output decreases substantially depending on the selenium doping concentration. A similiar dependence on the selenium doping concentration was observed for the process of light-output degradation in GaAsP: Se LED’s. It is proposed that gallium-vacancy selenium complexes are responsible for the observed phenomena.