利用MOVPE选区外延生长InGaAsP

研究了利用低压MOVPE宽条(15μm)选区外延生长InGaAsP的性质.研究了生长速率、厚度增强因子、带隙调制、组分调制随着生长条件如掩模宽度、生长压力、Ⅲ族源流量的变化规律,给出了合理的解释.同时研究了不同Ⅴ/Ⅲ比下选择性生长InGaAsP表面尖角的性质.     

Recent advances in metal-organic vapor phase epitaxy

Recent progress in the development and application of metal-organic vapor phase epitaxy (MOVPE) is reviewed. The formation of new and unique materials and structures, including wide-bandgap materials of both III-V and II-VI semiconductors, is discussed. The basic studies of the underlying chemistry and fluid flow behavior in MOVPE reactors and resulting improvements in the control of material properties and the uniformity of growth are considered. New growth precursors yielding both selective area growth and improved material purity are discussed. Improved reproducibility of the MOVPE growth product using growth monitors, for the real-time determination of film thickness and composition, which have resulted in greater acceptance of the MOVPE technique in the manufacturing environment, is discussed     

Model development of GaN MOVPE growth chemistry for reactor design

The metalorganic vapor phase epitaxy of GaN is complicated by the extensive and pervasive complex gas phase chemistry within the growth system. This gas phase chemistry leads to the high sensitivity of the material properties on the detailed fluid dynamics within the system. Computational fluid dynamics (CFD) based reactor modeling combined with gas phase kinetics studies was used to determine the transport and reaction behavior within a high performance vertical MOVPE reactor. The complexity of the growth chemistry model was increased in a step-wise fashion. At each step, the concentration profiles were determined using available recent kinetic data. The high gas flow rate typically employed in GaN MOVPE results in a very thin high-temperature flow sheet above the growth front, leading to an extremely high thermal gradient. Within this thin high-temperature flow sheet, a stratified chemical structure is formed as a result of the unique thermal fluid environment. This stratified structure is closely related to the transport and reaction behavior within GaN MOVPE processes and forms part of the engineering guidelines for GaN MOVPE reactor design.     

Selective MOVPE growth of InGaAsP and InGaAs using TBA and TBP

Selective metalorganic vapor phase epitaxial (MOVPE) growth of InGaAs(P) using tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) was systematically investigated for the first time. Selective growth was successfully achieved and the growth structure was as excellent as the structure using AsH₃/PH₃. Vapor phase lateral diffusion of group-III species, which is the major mechanism of selective MOVPE, can be easily controlled over the wide range of V/III ratio with using TBA/TBP. From this feature, we propose the selectively grown multiple quantum well waveguide structures which have excellent bandgap controllability by using TBA/TBP.     

The MOVPE community meets in Berlin

Berlin, host of this year's European Workshop on Metal-Organic Vapour Phase Epitaxy (EW MOVPE VII), is a city which has developed into one of the ‘centres of excellence’ in the field of MOVPE. An overview of MOVPE activities and related issues in the German capital — from basic growth studies to research and development of devices — is presented here.     

In-situ monitoring of surface stoichiometry and growth kinetics study of GaN (0001) in MOVPE by spectroscopic ellipsometry

GaN surface stoichiometry and growth kinetics in MOVPE were studied by in-situ spectroscopic ellipsometry. The effect of MOVPE conditions on both the surface stoichiometry and growth kinetics was investigated. The surface stoichiometry, such as N-rich, Ga-rich and Ga-excess surfaces, was monitored, and was drastically changed by the variation of the NH₃ partial pressure. When the TMG supply was interrupted during the growth, the layer-by-layer decomposition/revaporation was observed in H₂/NH₃ ambient. The decomposition rate was measured as a function of the NH₃ flow rate at the conventional epilayer growth temperatures (1050–1140 C). The decomposition rate was decreased with the increase in the N coverage on the GaN surface. it was found that the surface stoichiometry is a very important parameter for the control of the MOVPE growth kinetics.     

ZnO growth toward optical devices by MOVPE using N2O

Wide bandgap semiconductor zinc oxide (ZnO) layers were grown by metalorganic vapor phase epitaxy (MOVPE) using nitrous oxide (N₂O). Strong ultraviolet (UV) photoluminescence emissions with 1000 times less deep ones at room temperature were observed from ZnO layers grown on sapphire. Alow temperature (500 C)-grown buffer layer of ZnO was effective to enhance the initial nucleation process and to achieve high quality ZnO layers on it at higher growth temperatures (600–700 C). ZnO layers grown on III–V semiconductor substrates showed dominant UV luminescence in spite of low temperature growth. These results imply the abilities of high quality ZnO growth by MOVPE.     

Gallium nitride materials - progress, status, and potential roadblocks

Metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are the principal techniques for the growth and n-type (Si) and p-type (Mg) doping of III-nitride thin films on sapphire and silicon carbide substrates as well as previously grown GaN films. Lateral and pendeoepitaxy via MOVPE reduce significantly the dislocation density and residual strain in GaN and AlGaN films. However tilt and coalescence boundaries are produced in the laterally growing material. Very high electron mobilities in the nitrides have been realized in radio-frequency plasma-assisted MBE GaN films and in two-dimensional electron gases in the AlGaN/GaN system grown on MOVPE-derived GaN substrates at the crossover from the intermediate growth regime to the droplet regime. State-of-the-art Mg doping profiles and transport properties have been achieved in MBE-derived p-type GaN. The Mg-memory effect, and heterogeneous growth, substrate uniformity, and flux control are significant challenges for MOVPE and MBE, respectively. Photoluminescence (PL) of MOVPE-derived unintentionally doped (UID) heteroepitaxial GaN films show sharp lines near 3.478 eV due to recombination processes associated with the annihilation of free-excitons (FEs) and excitons bound to a neutral shallow donor (D/spl deg/X).     

Laser diodes integrated with butt-jointed spotsize converterfabricated on 2-in wafer

Laser diodes integrated with spotsize converters by butt-joint technology combined with selective area metal organic vapor phase epitaxial (MOVPE) growth have been successfully fabricated. Satisfactory uniformity, reproducibility (>99%) and tolerance for low threshold current, a narrow emitted beam, and low optical coupling loss to fiber (<-2.4 dB) are obtained by using 2-in full wafer fabrication technology in the experimental fabrication. To investigate the tolerance in fabrication, the characteristic dependence on the variation of the wet etching time just before the butt-joint MOVPE growth and also on the mesa stripe width are investigated. A wide tolerance for these fabrication parameters is confirmed. The results indicate that the butt-joint technology is a useful and reliable process for realizing spotsize converters of the present type and also suggest that the technology is widely applicable to various photonic integrated circuits     

Low temperature growth and characterization of ZnSe films grown on GaAs

Metalorganic vapor phase epitaxy (MOVPE) growth experiments of ZnSe on GaAs (100) are described using ditertiary butylselenide as the selenium source. The growth temperature was varied between 300 and 400°C and the growth rate was determined. Below a vapor pressure ratio P_Se/P_Zn of about 5, the selenium is the growth limiting component. The quality of the samples was analyzed by Nomarski microscopy, x-ray diffraction, high resolution transmission electron microscopy, and photoluminescence. Although the selenium-precursor was not specially purified, a sharp excitonic luminescence appears in samples grown at 400°C. The MOVPE growth of ZnSe still suffers from prereactions when H₂Se is used. The optimum growth is above 450°C even with precursors as DMSe or DESe which are less harmful than the hydride. This paper reports results obtained with a novel selenium-precursor: ditertiarybutylselenide.¹     

Criteria for versatile GaN MOVPE tool:high growth rate GaN by atmospheric pressure growth

Growth rate has a direct impact on the productivity of nitride LED production.Atmospheric pressure growth of GaN with a growth rate as high as 10μm/h and also Al_0.1Ga_0.9N growth of 1μm/h by using 4 inch by 11 production scale MOVPE are described.XRD of（002） and（102） direction was 200 arcsec and 250 arcsec, respectively.Impact of the growth rate on productivity is discussed.     

Low threshold operation of 1.55 μm GaInAsP/InP DFB-BH LDsentirely grown by MOVPE on InP gratings

1.55 μm GaInAsP/InP DFB-BH LDs on corrugated InP substrates were fabricated by only two-stage MOVPE including burying layer growth. The 9 mA minimum threshold current was achieved with both facets cleaved, which the authors believe is the lowest among MOVPE grown DFB LDs with InP grating. Up to 20 mW maximum output power and 0.21 W/A differential quantum efficiency were also attained under single longitudinal mode operation     

MOVPE生长Hg1-xCdxTe薄膜的实验研究

采用金属有机化合物汽相外延法(MOVPE)和多层膜互扩散生长工艺(IMP)在不同的生长条件下生长了许多Hg1-xCdxTe/GaAs(211)薄膜样品,并对样品进行了傅利叶红外透射(FTIR)和范德堡Hall测量;通过对许多实验数据进行系统的对比分析,总结了薄膜的生长规律,并对这些生长规律作出了理论分析,阐释了薄膜的微观生长机制.     

Normally Off n-Channel GaN MOSFETs on Si Substrates Using an SAG Technique and Ion Implantation

We have demonstrated n-channel gallium nitride (GaN) MOSFETs using a selective area growth (SAG) technique and ion implantation on a silicon substrate. Both MOSFETs realized good normally off operations. The MOSFET using the SAG technique showed a large drain current of 112 mA/mm, a lower leakage current, and a high field mobility of 113 cm²/V . s, which is, to our knowledge, the best for a GaN MOSFET on a silicon substrate.     

HgCdTe growth on (552) oriented CdZnTe by metalorganic vapor phase epitaxy

We report the growth of HgCdTe on (552)B CdZnTe by metalorganic vapor phase epitaxy (MOVPE). The (552) plane is obtained by 180 rotation of the (211) plane about the [111] twist axis. Both are 19.47 degrees from (111), but in opposite directions. HgCdTe grown on the (552)B-oriented CdZnTe has a growth rate similar to the (211)B, but the surface morphology is very different. The (552)B films exhibit no void defects, but do exhibit ∼40 μm size hillocks at densities of 10–50 cm⁻². The hillocks, however, are significantly flatter and shorter than those observed on (100) metalorganic vapor phase epitaxy (MOVPE) HgCdTe films. For a 12–14 μm thick film the height of the highest point on the hillock is less than 0.75 μm. No twinning was observed by back-reflection Laue x-ray diffraction for (552)B HgCdTe films and the x-ray double crystal rocking curve widths are comparable to those obtained on (211)B films grown side-by-side and with similar alloy composition. Etch pit density (EPD) measurements show EPD values in the range of (0.6–5)×10⁵ cm⁻², again very similar to those currently observed in (211)B MOVPE HgCdTe. The transport properties and ease of dopant incorporation and activation are all comparable to those obtained in (211)B HgCdTe. Mid-wave infrared (MWIR) photodiode detector arrays were fabricated on (552)B HgCdTe films grown in the P-n-N device configuration (upper case denotes layers with wider bandgaps). Radiometric characterization at T=120–160 K show that the detectors have classical spectral response with a cutoff wavelength of 5.22 μm at 120 K, quantum efficiency ∼78%, and diffusion current is the dominant dark current mechanism near zero bias voltage. Overall, the results suggest that (552)B may be the preferred orientation for MOVPE growth of HgCdTe on CdZnTe to achieve improved operability in focal plane arrays.     

基于图形衬底生长的GaN位错机制分析

采用缺陷选择性腐蚀法结合光学显微镜及原子力显微镜(AFM)对金属有机化合物气相外延(MOVPE)在蓝宝石图形衬底(PSS)上生长的非掺杂GaN体材料的位错产生机制进行了研究,分析结果表明,位错来源于三个方面:一是"二步法"生长机制引入的位错;二是是由于图形衬底上不同区域GaN晶体相互连接时由于晶面不连续所造成的位错群;三是由于图形衬底制作工艺过程中引入的表面污染与损伤.     

MOVPE-grown 1.5 µm distributed feedback lasers on corrugated InP substrates

A single-step low-pressure metalorganic vapor phase epitaxy (MOVPE) was applied to the fabrication of 1.5 μm InGaAsP/InP distributed feedback laser diodes on corrugated InP substrates, accompanied by LPE for buried heterostructure formation. High probability of single longitudinal mode operation was obtained due to the uniformity of the active layer thickness. A typical threshold current was 35 mA with both facets cleaved. A maximum output power of up to 27 mW was also obtained under single longitudinal mode operation with anti-reflective/cleaved facet configuration. The laser diode had high spectral stability under high-frequency direct modulation of 1.4 GHz. Results of initial aging tests (APC of 5 mW at 25°C for longer than 3800 h) have shown no degradation in driving currents. It is found that low-pressure MOVPE is favorable for epitaxial growth on corrugated substrates.     

Optoelectronic integrated circuit (OEIC) waveguide coupler for spotsize expansion and improved fibre coupling efficiency

An MOVPE vertical coupler structure is used to provide efficient coupling between InP/InGaAsP optoelectronic integrated circuit (OEIC) waveguides and cleaved monomode fibres. A 2 dB improvement in the coupling efficiency of TE polarised light of wavelength 1.55 μm is demonstrated. The structure does not require any additional growth steps, and is compatable with vertically integrated detector structures     

High quality GaAs/AlGaAs quantum wells grown on (111)A substrates by metalorganic vapor phase epitaxy

Growth of GaAs and AlGaAs epitaxial layers on both (111)A and (111)13 faces of GaAs substrates was studied by the atmospheric metalorganic vapor phase epitaxy (MOVPE) technique. We show that GaAs and AlGaAs layers with excellent surface quality can be grown at relatively low temperatures and V/III ratios (600°C, 15) on the (111)A face, whereas for layers on the (111)13 face a higher growth temperature (720°C) was required. GaAs/AlGaAs quantum well (QW) structures were successfully grown for the first time on the (111)A GaAs face by the MOVPE technique. The effects of various growth conditions on the surface morphology of the epilayers were studied. For the (111)A surface a wide growth window with temperatures in the range 600°-660°C and V/III ratios varying from 15 to 45 was established for obtaining excellent surface morphology. The properties of the QWs were investigated by high resolution X-ray diffractometry, photoluminenscence and photoreflectance measurements. These measurements indicate that the QWs are of very high structural and optical quality.     

Anisotropy in selective metalorganic vapor phase epitaxy of CdTe on GaAs and Si substrates

CdTe epitaxial layers are grown by metalorganic vapor phase epitaxy (MOVPE) on patterned (100) Si and (100) GaAs substrates using SiO₂, Si₃N₄ or CaF₂ masks. Selective epitaxy of CdTe can be achieved by using Si₃N₄ and CaF₂ masks and by controlling the growth conditions during MOVPE. The selectively grown CdTe layers show strong anisotropy depending on the orientation of the window pattern on the mask, as well as on the orientation of the starting substrates. CdTe with smooth atomically flat surfaces and vertical side walls can be obtained on (100) GaAs substrates by suitably orienting the window pattern directions and optimizing the growth conditions. For the growth conditions that are suitable for the selective growth, the growth is mass-transfer limited. The lateral growth rate depends on the ratio of the window width to the mask width. Use of CaF₂ allows wider temperature window for selective growth since no nucleation was observed on CaF₂ even at 450°C.