MBE生长高质量GaAs／AlGaAs量子阱激光器

我们利用分子束外延方法研制了ＧａＡｓ／ＡｌＧａＡｓ缓交折射率分别限制（ＧＲＩＮ－ＳＣＨ）单量子阱和双量子阱激光器．对腔长为６００μｍ的端面不镀膜的宽接触条型Ｆ－Ｐ腔激光器，阈值电流密度（平均值）分别为２９０Ａ／ｃｍ２和２４０Ａ／ｃｍ２．腔长在１２００μｍ的双量子阱激光器的阈电流密度低达１９０Ａ／ｃｍ２．对出光面和背面分别镀以增透膜和高反膜的宽接触条型（８０μｍ）．激光器，线性输出功率高达１．８２Ｗ；出光面的斜率效率达到１．０４Ｗ／Ａ；利用湿法化学腐蚀所制备的脊形波导结构单量子阱激光器阈值电流最低可达８ｍＡ     

InGaAs/AlGaAs应变量子阱激光器的可靠性

利用分子束外延方法研制的ＩｎＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器外延材料制备了窄条型脊型波导结构量子阱激光器件．通过对其５０℃高温加速老化,检测了器件的可靠性,并对器件中存在的三种典型退化行为,即快速退化、慢退化和端面光学灾变损伤进行了分析与研究．     

2微米AlGaAsSb/InGaSb I类量子阱大功率激光器

通过分子束外延的方式生长了2微AlGaAsSb/InGaSb I类量子阱大功率激光器。制备了脊条形波导的激光二极管以及激光器线列（4个发射单元）,腔面均未镀膜。对单个激光二极管,在10℃工作温度下,最大连续激射功率为0.5W,阈值电流密度为150A/cm2,斜率效率为0.17W/A,在脉冲宽度为100微秒,5%占空比的条件下,其脉冲光功率达到0.98W。对激光器线列,室温最大连续激射功率为1.02W,最大脉冲激射功率达到3.03W。     

MBE生长InGaAs／GaAs应变层单量子阱激光器结构材料的研究

采用ＶａｒｉａｎＧｅｎⅡＭＢＥ生长系统研究了ＩｎＧａＡｓ／ＧａＡｓ应变层单量子阶（ＳＳＱＷ）激光器结构材料。通过ＭＢＥ生长实验，探索了Ｉｎ＿ｘＧａ＿（１－ｘ）ｔＡｓ／ＧａＡｓＳＳＱＷ激光器发射波长（λ）与Ｉｎ组分（ｘ）和阱宽（Ｌ＿ｚ）的关系，并与理论计算作了比较，两者符合得很好。还研究了材料生长参数对器件性能的影响，主要包括：Ⅴ／Ⅲ束流比，量子阱结构的生长温度Ｔ＿ｇ（ＱＷ），生长速率和掺杂浓度对激光器波长、阈值电流密度、微分量子效率和器件串联电阻的影响。以此为基础，通过优化器件结构和ＭＢＥ生长条件，获得了性能优异的Ｉｎ＿（０．２）Ｇａ＿（０．８）Ａｓ／ＧａＡｓ应变层单量子阱激光器：其次长为９６３ｎｍ，阈值电流密度为１３５Ａ／ｃｍ￣２，微分量子效率为３５．１％。     

MBE生长温度对InGaAs／GaAs应变单量子阱激光器性能的影响

采用分子束外延（ＭＢＥ）技术，研制生长了ＩｎＧａＡｓ／ＧａＡｓ应变单量子阱激光器材料，并研究了生长温度及界面停顿生长对激光器性能的影响。结果表明，较高的ＩｎＧａＡｓ生长温度和尽可能短的生长停顿时间，将有利于降低激光器的阈值电流。所外延的激光器材料在２５０μｍ×５００μｍ宽接触、脉冲工作方式下测量的阈电流密度的典型值为１６０ｍＡ／ｃｍ２。用湿法腐蚀制作的４μｍ条宽的脊型波导激光器，阈值电流为１６ｎＡ，外微分量子效率为０４ｍＷ／ｍＡ，激射波长为９７６±２ｎｍ，线性输出功率为１００ｍＷ。     

分子束外延生长高应变单量子阱激光器

采用分子束外延方法研究了高应变 In Ga As/Ga As量子阱的生长技术 .将 In Ga As/Ga As量子阱的室温光致发光波长拓展至 116 0 nm,其光致发光峰半峰宽只有 2 2 me V.研制出 112 0 nm室温连续工作的 In Ga As/Ga As单量子阱激光器 .对于 10 0 μm条宽和 80 0 μm腔长的激光器 ,最大线性输出功率达到 2 0 0 m W,斜率效率达到 0 .84m W/m A,最低阈值电流密度为 45 0 A/cm2 ,特征温度达到 90 K.     

分子束外延生长高应变单量子阱激光器

采用分子束外延方法研究了高应变InGaAs/GaAs量子阱的生长技术.将InGaAs/GaAs量子阱的室温光致发光波长拓展至1160nm,其光致发光峰半峰宽只有22meV.研制出1120nm室温连续工作的InGaAs/GaAs单量子阱激光器.对于100μm条宽和800μm腔长的激光器,最大线性输出功率达到200mW,斜率效率达到0.84mW/mA,最低阈值电流密度为450A/cm2,特征温度达到90K.     

980nm高功率应变量子阱阵列激光器的研制

利用分子束外延（MBE）方法研制出了高质量的InGaAs/GaAs/AlGaAs应变量子阱阵列激光器。其有源区采用分别限制单量子阱结构，激射波长在980nm左右，阵列器件由48个LD构成，在重复频率300Hz、脉冲宽度200μs的条件下，定温光功率输出达到20W，斜率效率1.1W/A，光电转换效率29％。     

Molecular beam epitaxy growth of InGaSb/AlGaAsSb strained quantum well diode lasers

2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K.The optimal growth temperature of quantum wells is 440℃.The PL peak wavelength of quantum wells at 300 K is 1.98μm,and the FWHM is 115 nm.Tellurium-doped GaSb buffer layers were optimized by Hall measurement.The optimal doping concentration is 1.127×10¹⁸ cm^-3 and the resistivity is 5.295×10^-3Ω·cm.     

OMVPE growth of GaInAsSb/AlGaAsSb for quantum-well diode lasers

GaInAsSb and AlGaAsSb alloys have been grown by organometallic vapor phase epitaxy (OMVPE) using all organometallic sources, which include tritertiarybutylaluminum, triethylgallium, trimethylindium, tertiarybutylarsine (TBAs), and trimethylantimony. Excellent control of lattice-matching both alloys to GaSb substrates is achieved with TBAs. GaInAsSb/AlGaAsSb multiple quantum well (MQW) structures grown by OMVPE exhibit strong 4K photoluminescence with full width at half maximum of 10 meV, which is comparable to values reported for quantum well (QW) structures grown by molecular beam epitaxy. Furthermore, we have grown GaInAsSb/AlGaAsSb MQW diode lasers which consist of n- and p-doped Al_0.59Ga_0.41As_0.05Sb_0.95 cladding layers, Al_0.28Ga_0.72As_0.02Sb_0.98 confining layers, and four 15 nm thick Ga_0.87In_0.13As_0.12Sb_0.88 quantum wells with 20 nm thick Al_0.28Ga_0.72As_0.02Sb_0.98 barrier layers. These lasers, emitting at 2.1 μm, have exhibited room-temperature pulsed threshold current densities as low as 1.2 kA/cm².     

Growth of InAIGaAs strained quantum well structures for reliable 0.8 μm lasers

Incorporation of indium into the quantum well materials of graded-index separate confinement heterostructure quantum well lasers has proven to be a key to imparting a much needed robustness to such lasers. By growing wells which contain both indium and aluminum along with gallium, operating wavelengths can be engineered to fall in the technologically important range of 0.8 microns, appropriate for pumping Nd:YAG. The organometallic vapor phase epitaxial growth of these strained-layer structures faces extra challenges rooted in the competing influences on the energies of the quantized states. At a minimum, meeting wavelength targets requires achieving control of the quaternary composition and of the quantum well thickness. Because laser elements are relatively large, lateral uniformity of wavelength is a critical issue. Device performance is influenced by basic material quality, which is a function of such fundamental growth parameters as temperature, V/III ratio, and growth rate. We have grown InAIGaAs structures using various combinations of growth conditions and well composition and thickness combinations, and evaluated and life-tested lasers in CW mode. The reactor’s performance in achieving composition and thickness uniformity is reported, as are data on the influence of the effects of growth conditions on device performance.     

The use of computer controlled group V valved sources for interface type control in InGaSb/InAs strained layer superlattices

The purpose of this research is to demonstrate the necessity of computer controlled valved group V effusion cell sources in the growth of indium gallium antimonide/indium arsenide (InGaSb/InAs). These sources allow enhanced control of the group V flux. This flux control allows the reduction of unwanted cross contamination and complete control of the interface type. For simple structures, this control can be done manually, however, for complicated structures the control must be automated to allow for reproducibility and uniformity. The InGaSb/InAs strained layer superlattice (SLS) is an example of a complicated structure with hundreds of layers that requires interface type control. Arsenic incorporation with typical flux shuttering was found to be a problem in the growth of antimonide layers and limit interface type control. The antimony incorporation was not found to occur for the growth of arsenide layers. In addition, antimony exposure to critical interfaces did not appear to reduce the interface quality. This research demonstrates that the use of computer controlled valve sources is only required for the arsenic source when attempting to create InGaSb/InAs SLS structures.     

Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (h _c) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In_0.11Ga_0.89As, in which the QW layers are under biaxialcompression, and Al_0.35Ga_0.65As/GaAs_0.82P_0.18, in which the QW layers are under biaxialtension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800–850° C had no significant effect on the PL spectra, signifying that even layers that have exceededh _c and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.     

MOVPE growth of AlGaAs/GaInP diode lasers

GaAs-based diode lasers for emission wavelengths between 800 nm and 1060 nm with AlGaAs-cladding and GaInP-waveguide layers were grown by MOVPE. For wavelengths above 940 nm broad area devices with InGaAs QWs show state-of-the-art threshold current densities. Ridge-waveguide lasers fabricated by selective etching achieve 200 mW CW monomode output powers. (In)GaAsP QW-based diode lasers with an emitting wavelengths around 800 nm suffer from problems at the upper GaInP/AlGaAs interface. Asymmetric structures with a lower AlGaAs/GaInP and an upper AlGaAs/AlGaAs waveguide not only avoid this interface but also offer better carrier confinement. Such structures show very high slope efficiencies and a high T₀. Maximum output powers of 7 W CW are obtained from 4 mm long devices.     

Photoluminescence excitation spectroscopy of InAs0.67P0.33/InP strained single quantum wells

The optical emission characteristics of biaxially compressed InAs _x P_{1− x} /InP strained single quantum well (QW) structures, with nominal compositionx=0.67, have been investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The highly strained QWs exhibit intense and narrow PL in the 0.9–1.5 μm wavelength range, similar to the lattice-matched InGaAs(P)/InP system. The 20 K PLE spectra exhibit well-resolved features attributed ton=1 heavy hole (E1H1) and light hole (E1L1) transitions in the 1.0–1.5 μm wavelength range. In addition, features attributed to transitions betweenn=2 electrons and heavy holes (E2H2), and betweenn=1 electrons and unconfined holes (E1Hf), were observed. The energy splitting between the heavy-hole and light-hole bands was found to be a sensitive measure of the band offsets in the system. The best prediction of this splitting was obtained for a valence band offset of δE _V ∼0.25δE _G . This value of band offset was in agreement with the energy position of the E1Hf transition. The observed transition energies were also compared with the results of a finite square well model, taking into account the effects of strain, and the results offer further support for the band offset assignment. This study indicates that the InAsP system may be advantageous for application in strained-layer optoelectronic devices operating in the 1.3–1.6 μm wavelength range.     

Molecular beam epitaxial growth of strained AIGalnAs multi-quantum well lasers on InP

State of the art transparency currents as low as 41 A/cm² per well have been achieved in strained AIGalnAs multi-quantum well (MQW) 1.5 urn lasers. Grown by solid source molecular beam epitaxy, broad area lasers with seven quantum wells exhibit threshold current densities of less than 900 A/cm² for a 300 μm device length, comparable to the best results in this material system by any growth technology. The key to this threshold current density reduction is the optimization of the quantum well width. Experimentally, we found that thresh-old current densities can be reduced by a factor of two by using MQW active regions with wider wells which we attribute to a reduction in the nonradiative recombination and improved electron-hole overlap. High resolution x-ray diffraction, photoluminescence, and broad area lasers were used to characterize the MQW active regions.     

Highly strained ln0.35Ga0.65As/GaAs layers grown by molecular beam epitaxy for high hole mobility transistors

We have grown highly strained In_0.35Ga_0.65As layers on GaAs substrates by molecular beam epitaxy to improve the performance of high hole mobility transistors (HHMTs). The mobility and sheet hole concentration of double side doped pseudomorphic HHMT structures at room temperature reached 314 cm2/V-s and 1.19 × 10¹² cm⁻², respectively. Photoluminescence measurements at room temperature show good crystalline quality of the In^0.35Ga_0.65As layers. This study suggests that the performance of HHMTs can be improved by using high-quality In_0.35Ga_0.65As layers for the channel of double side doped heterostructures pseudomorphically grown on GaAs substrates.     

A novel current injected strained quantum well laser grown by MOVPE

Conventional long wavelength (1.3 and 1.55 μm emitting) GalnAsP alloy lasers suffer from two disadvantages. Firstly, carriers in the highest lying valence band have a heavy effective mass relative to carriers in the conduction band. This asymmetry leads to an increase in the carrier density required for lasing action to occur. Secondly, non-radia-tive recombination processes, such as Auger Recombination (AR) and Inter Valence Band Absorption (IVBA), which involve occupancy of the heavy-hole (HH) states, are thought to be significant in these materials. These again lead to higher thresholds and lower values ofT ₀than might otherwise be the case. Recently, there has been considerable interest in the prospect of “engineering” the band structure of a 1.5 μm emitting device so as to overcome these problems. It has been reported that for a quantum well under biaxial compression, the light-hole/heavy-hole (LH/HH) degeneracy at the gamma point will be lifted such that the highest lying valence band will be LH-like in the in-plane direction. This should reduce both the effective mass asymmetry and the thermal occupancy of the HH states, lowering the threshold carrier density and reducing the AR and IVBA rates. This paper describes MOVPE growth and characterisation of the first 1.55 μm emitting current injected strained layer laser structure. The active region contains 3.5 nm thick strained quantum wells of Ga_o.3In_o.7As situated in the central region of a quaternary waveguide and grown on InP. TEM micrographs and x-ray data demonstrate that the lattice mismatch (approximately 1%) has been accommodated elastically, without the formation of misfit dislocations. Broad area lasers have been fabricated with lengths of 200–1200 μm and threshold current densities as low as 930 Acm^-2 have been measured from the longer devices. Similar 1.55 μm emitting structures containing unstrained 7.5 nm thick Ga_o.47In_o.53As wells have also been grown and characterised for comparison. As yet, no significant improvement in either threshold current orT ₀has been observed for strained lasers over unstrained devices.