Laser excitation induced photoluminescence linewidth reduction in molecular beam epitaxial InAlAs layers grown on InP substrates

An experimental investigation is presented on the influence of laser excitation on the photoluminescence (PL) linewidth in InAlAs layers grown lattice matched to InP substrates by molecular beam epitaxy (MBE). Measurements performed on silicon-doped samples and samples grown at different arsenic overpressures (V/III flux ratio) showed that the linewidth decreases with increasing laser excitation power. A model describing an unbalanced migration of photo-generated charge carriers due to the presence of clusters is proposed to explain the effect of the linewidth reduction. Also, the trend of the linewidth decrease becomes more pronounced in InAlAs samples with higher silicon doping concentrations and those grown at higher V/III ratios. Samples with higher silicon-doping concentrations have broader linewidths which could be the result of poorer alloy quality due to the presence of disorder (S. F. Yoon et al., J. Appl. Phys. 78, 1812 (1995)). A similar trend of linewidth reduction was observed at temperatures as high as 30 K. Our results show that such a measurement of linewidth vs. laser excitation power can be used as a supplementary method for InAlAs material characterization.     

Growth of In0.52Al0.48As on InP substrates by molecular beam epitaxy: some effects of V/III flux ratio variation

Growth of In_0.52Al_0.48As epitaxial layers on InP(100) substrates by molecular beam epitaxy at a wide range of arsenic overpressure (V/III flux ratio from 30 to 300) is carried out. Analysis performed using low-temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) showed a strong and prominent dependence of the PL and XRD linewidths on the V/III flux ratio. Under our growth conditions, both the PL and XRD linewidths exhibit a minimum point at a V/III flux ratio of 150 which corresponds to a maximum in the PL intensity and XRD intensity ratio. Flux ratios exceeding 150 results in an increase in both the PL and XRD linewidths corresponding to a reduction in their associated intensities. Room-temperature Raman scattering measurements show a narrowing in the InAs-like and AlAs-like longitudinal-optic (LO) phonon linewidths which broaden at high flux ratios, while the LO phonon frequencies exhibit a gradual reduction as the flux ratio is increased. PL spectrum taken at increasing temperature show a quenching of the main emission peak followed by the evolution of a broad lower energy emission which is possibly associated with deep-lying centres. This effect is more prominent in samples grown at lower V/III flux ratios. Hall effect measurements showed a gradual reduction in the mobility in correspondence to an increase in the electron concentration as the flux ratio is increased.     

On factors affecting alloy clustering in In0.52Al0.48As layers grown on InP substrates by molecular beam epitaxy

Growth of In_0.52Al_0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate temperatures (470 - 550 °C) and V/III flux ratios is carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) measurements showed a strong dependence of the PL and XRD linewidths and lattice-mismatch on the substrate temperature. Minimum PL and XRD linewidths and lattice-mismatch were found to occur at substrate temperatures between ≈ 500 - 520 °C. The XRD intensity ratios (I_epi/I_sub) were generally higher within the same substrate temperature range at which the lattice-mismatch was the lowest. XRD rocking-curves of samples grown at low temperatures showed the main epilayer peak to be a composition of smaller peaks which can strongly indicate the presence of alloy clustering. PL spectra taken at increasing temperatures showed the quenching of the main emission peak followed by the evolution of a distinct peak at lower energy, possibly associated with carrier localization due to the presence of lattice disorder. Within the range of V/III flux ratios investigated (32 to 266), the lowest PL linewidth of 14 meV was recorded for the samples grown at a V/III ratio of 160. The lattice-mismatch between the epilayer and the substrate for these samples was also found to be relatively insensitive to changes in the V/III flux ratios.     

Single-well resonant-tunneling diode heterostructures based on In0.53Ga0.47As/AlAs/InP with the peak-to-valley current ratio of 22:1 at room temperature

Current-voltage (I–V) characteristics of resonant-tunneling diode In_0.53Ga_0.47As/AlAs/InP structures are studied at 300 and 77 K. The peak-to-valley current ratios were determined as 22:1 and 44:1 at temperatures of 300 and 77 K, respectively, which correspond to the maximum values for InGaAs/AlAs/InP heterostructures without an additional InAs layer of a quantum subwell in their configuration.     

Magnesium doping in InAlAs and InGaAs/Mg films lattice-matched to InP grown by MOVPE

Mg-doped InAlAs and InGaAs films were grown at 560 °C lattice matched to InP semi-insulting substrate by metalorganic vapor phase epitaxy (MOVPE) under various Cp₂Mg flow conditions. Hall effect, photoluminescence (PL), high-resolution X-ray diffraction (HR-XRD), and secondary ion mass (SIMS) were the tools used in this work. The crystalline quality and the n-p conversion of the InAlAs and InGaAs/Mg films are described and discussed in relation to the Cp₂Mg flow. Distinguishing triple emission peaks in PL spectra is observed and seems to be strongly dependent on the Cp₂Mg flow. SIMS is employed to analyze the elements in the epitaxial layers. The variation of indium and magnesium components indicates a decrease of magnesium incorporation during the growth of InAlAs layers leading to a contracted lattice. In addition, the magnesium incorporation in the InGaAs lattice during growth has been confirmed by SIMS.     

MBE生长的In_(1-x-y)Ga_xAl_yAs/InP四元混晶的拉曼散射

ＭＢＥ生长的Ｉｎ１－ｘ－ｙＧａｘＡｌｙＡｓ／ＩｎＰ四元混晶的拉曼散射韩和相汪兆平李国华徐士杰刘南竹朱作明（中国科学院半导体研究所半导体超晶格国家重点实验室北京１０００８３）ＯｐｔｉｃａｌＰｈｏｎｏｎＲａｍａｎＳｃａｔｅｒｉｎｇｆｒｏｍＩｎ１－ｘ－ｙＧ...     

InGaAs(P)/InP MQW mixing by Zn diffusion,Ge and S implantation for optoelectronic applications

There is a growing interest in impurity-induced layer disordering for the technologically important InGaAs(P)/InP system. More complicated than in the AlGaAs/GaAs ternary system, which concerns only interdiffusion of group III atoms, interdiffusion in this quaternary system can occur for both group III (Ga,In) and group V (P,As) atoms, which may or may not result in a strain-free alloy lattice-matched to InP, a major concern for device applications. After a brief review on the thermal stability of InP/ InGaAs quantum well structures, we show that Zn diffusion at moderate temperature leads to intermixing on the group III sublattice, only, with subsequent lattice mismatch. On the other hand, either Ge or S implantation of InGaAs/InP quantum wells results in intermixing involving both the group III and the group V sublattice and approximating the lattice-matched condition.     

GaAs-InP异质材料的结构特性和光学特性研究

我们在低压金属有机汽相沉积(MOCVD)设备上采用两步升温法与金属有机源流量周期调制生长界面过渡层方法制备出GaAs-InP材料,并对此进行了X-射线衍射、低温光致发光谱(PL)和Raman谱分析,结果表明,GaAs外延层的位错密度低于用两步升温法得到的GaAs材料,PL谱峰较强,GaAs的特征激子峰和杂质相关的激子峰同时被测到。Raman谱PL谱的峰移表明GaAs外延层处于(100)双轴伸张应力下,应力大小随温度变化是由于GaAs、InP之间的热膨胀系数不同。     

A Raman study of the strain in InP/GaAs heterostructures grown by MOVPE

A Raman investigation on InP layers grown by Metal Organic Vapour Phase Epitaxy on GaAs (001) substrates, with thicknesses exceeding the critical thickness and ranging from 23 to 280 nm, is reported. The InP LO phonon shows an increasing frequency blue-shift with decreasing layer thickness, indicating a residual compressive strain due to the lattice mismatch and to the difference between the thermal expansion coefficients of InP and GaAs.     

Tight-binding design of intersubband transitions in InGaAs/AlAs quantum heterostructures grown pseudomorphically on InP

Intersubband optical properties of InGaAs/AlAs quantum heterostructures grown on InP are analysed. Our calculations based on a recently developed empirical tight-binding model show that the system is ideally suited for the tailoring of optical properties in a wide range. In particular, structures matching the frequency requirements of ultra-fast fibre optics communications are presented and discussed.     

Abnormal temperature dependence of photoluminescence from self-assembled InAs quantum dots covered by an InAlAs/InGaAs combination layer

In this report we have investigated the temperature dependence of photoluminescence (PL) from self-assembled InAs quantum dots (QDs) covered by an InAlAs/InGaAs combination layer. The ground state experiences an abnormal variation of PL linewidth from 15 K up to room temperature. Meanwhile, the PL integrated intensity ratio of the first excited state to the ground state for InAs QDs unexpectedly decreases with increasing temperature, which we attribute to the phonon bottleneck effect. We believe that these experimental results are closely related to the partially coupled quantum dots system and the large energy separation between the ground and the first excited states.     

Influence of Ⅴ/Ⅲ ratio on the structural and photoluminescence properties of In0.52AlAs/In0.53GaAs metamorphic high electron mobility transistor grown by molecular beam epitaxy

A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic force microscopy （AFM）, Hall measurement, and low temperature photoluminescence （PL）. The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square （RMS） roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/（V.s） and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed.     

MOCVD-GaxIn1-xAsyP1-y/InPDBR结构的晶格振动

利用微区Raman散射技术研究了MOCVD-Ga_xIn_1-xAs_yP_1-y/InPDBRs结构的晶格振动。在InP衬底上生长的与InP晶格匹配的四元合金Ga_0.4In_0.6As_0.85P_0.15中包含三种主要的振动模式,分别归属于类InAs、类GaAs和类GaInP。随着Ga_0.4In_0.6As_0.85P_0.15与InP交替生长构成的DBRs结构周期数增加,Raman散射谱中三种振动模式的谱线线型发生明显变化,类InAs振动强度不变,谱线窄化,峰值位置向低频方向移动,类GaAs和类GaInP振动强度逐渐减弱。同时类InAs与类GaAs振动强度比增大。Raman散射研究中声子的限制效应表明多层结构生长过程中界面存在非完整晶态。     

InAlAs/GaSbAs/InP DHBT与InP/GaSbAs/InP DHBT性能比较分析

双异质结双极晶体管(DHBT)的性能与发射区-基区(E-B) 异质结和基区-集电区(B-C)异质结的能带突变类型关系密切, 本文基于热场发射-扩散模型, 对两类不同能带结构类型的新型DHBT的性能做了比较分析. 结论表明: 与作为当今研究热点的E-B和B-C异质结构均为全交错II型能带结构的InP/GaSbAs/InP DHBT的性能相比, E-B异质结采用传统I型、B-C异质结采用交错II型的一类新型能带结构的InAlAs/GaSbAs/InP DHBT虽然在开启电压上更高, 但具有更好的电流驱动能力、直流增益和高频性能.     

Pressure reduction of parasitic parallel conduction in InGaAs/InP heterostructures containing LT-InP layers

Abstract

We have measured classical and quantum (Shubnikov-de Haas effect) magnetotrans-port properties of InGaAs/InP heterostructures in which phosphorus antisite defects incorporated in low temperature MBE-grown InP (LT-InP) layers are the main source of electrons. The heterostructures show strong parasitic parallel conduction, which is reduced under hydrostatic pressure. The comparison of the experimental results with the calculations of the potential profile and the charge distribution in the heterostructures enables to identify all the conduction channels in the structures and unambiguously proves that the parasitic parallel conduction is due to spontaneous formation of the quantum well in the LT-InP buffer.     

Analysis of room temperature PL spectra of InAs/GaAs/InP and InAs/InP self-assembled QDs: A five-band study

In this paper, room temperature PL spectra of InAs self-assembled dots grown on GaAs/InP and InP substrate are presented. For analyzing different positions of the PL peaks, we examine the strain tensor in these quantum dots (QDs) using a valence force field model, and use a five-band k·p formalism to find the electronic spectra. We find that the GaAs tensile-stained layer affects the position of room temperature PL peak. The redshift of PL peak of InAs/GaAs/InP QDs compared to that of InAs/InP QDs is explained theoretically.     

Growth mode and effect of carrier gas on In0.53Ga0.47As/InP surface morphology grown with trimethylarsine and arsine

Different growth mode have been observed for InGaAs/InP grown with trimethylarsine and arsine by Metalorganic Vapor Phase Epitaxy (MOVPE) when changing the carrier gas. The surface has been investigated by Atomic Force Microscope (AFM) for epilayers grown at 600°C under pure hydrogen or a mixture of hydrogen and nitrogen as carrier gas. The step/terrace surface morphology was observed for InP/InP and InGaAs/InP (001) using 0.2° off substrates. InP epilayers grown under nitrogen flow show step-bunched terraces as large as 170 nm. The effect of the group V source for InGaAs/InP has been studied. It is shown that the step edge characteristic of step flow growth appears for lattice-matched InGaAs/InP grown with arsine. When using TMAs and hydrogen as a carrier gas, the growth mode and surface roughness depends greatly on V/III ratio and growth temperature. Under nitrogen flow with the combination of TMI+TMG+TMAs, pit-like defects (5–8 nm deep) are visible at high surface concentration (10⁹–10¹⁰/cm²). When increasing V/III ratio, 3D growth occurs simultaneously with pit-like defects, recovering the whole surface of the sample. Various surface morphology characteristics of InGaAs epilayers assessed by AFM characterisation will be presented and discussed.     

Residual strain and alloying effects on the vibrational properties of step-graded InxAl1−xAs layers grown on GaAs

Lattice-relaxed In_xAl_1−xAs-graded buffer layers grown by MBE on GaAs substrate have been studied by micro-Raman scattering and photoluminescence (PL). In these heterostructures, the indium composition was gradually increased in six or four intermediate layers each of 100 nm thickness. The alloying effect in the In_xAl_1−xAs layers has been interpreted using the modified random element isodisplacement (MREI) formalism. The dependence in the MREI model of the longitudinal optical (LO) phonon energy and the In composition in the InAlAs alloy with PL measurements and Raman analysis allow the evaluation of disorder degree and give the In composition in the InAlAs active layers. The obtained InAs- and AlAs-like phonon frequencies from the fitting of Raman spectra are in reasonable agreement with those calculated according to the MREI model. Raman spectra show that InAs-like phonon frequencies are not strongly dependent either on the buffer structure or on the residual strain in the active layers. Using the AlAs-like LO phonon frequency shifts, we have calculated the residual strain in the In_xAl_1−xAs active layer. Raman results show that the slope of the grade is an important parameter that allows the growth of samples with good quality. The lower residual strain value was obtained by thick buffer with a smaller grading rate. PL measurements show that In compositions of active layers of the different studied samples are slightly higher than those measured during growth.     

Crystallinity and interdiffusion in InP/InGaAs quantum wells grown by Hydride VPE

This paper reports the results of a study on interfacial quality and thermal interdiffusion for InP/InGaAs Quantum Wells (QW) grown by hydride VPE. By controlling well layer as thin as 25 Å, it was estimated that island and valley, whose height was one monolayer and whose lateral size was one third of exciton radius, existed at the interface. For the first time, interdiffusion coefficients for InP/InGaAs QW were obtained from 77K PL peak energy shift. Typical values were 2.5×10⁻¹⁹ cm²/sec and 1.5×10⁻¹⁸ cm²/sec for the annealing temperature of 700°C and 750°C, respectively. These values are over 10² times larger than that in AlGaAs/GaAs QW, and less 10⁻² times smaller than that in InAlAs/InGaAs QW.     

Structure and photoluminescence study of type-II GaAs quantum wires and dots grown on nano-faceted (3 1 1)A surface

(3 1 1)A GaAs/AlAs corrugated superlattices (CSLs) and satellite (3 1 1)B and (1 0 0) SLs were studied using Raman spectroscopy, high-resolution transmittance electron microscopy (HRTEM) and photoluminescence (PL). The thickness of GaAs layers was varied from 1 monolayer (ML) to 10 ML, the thickness of AlAs barriers was 10 ML in (3 1 1) direction. The strongest modification of the Raman spectra is found for the case of partial (<1 nm) GaAs filling of the AlAs surface. The calculated and experimental Raman spectra demonstrated a good agreement for both complete (1 nm) and partial (<1 nm) GaAs filling of the AlAs surface. According to Raman and HRTEM data, in the case of partial filling of (3 1 1)A AlAs surface, GaAs forms quantum well wires of finite length (quantum dots). A drastic difference of PL from grown side-by-side (3 1 1)A and (3 1 1)B SLs was observed. A strong room temperature PL in the green–yellow spectral region was observed in GaAs/AlAs (3 1 1)A CSLs containing GaAs type-II quantum dots.