共查询到20条相似文献,搜索用时 15 毫秒
1.
Neal G. Anderson Farid Agahi Arvind Baliga Kei May Lau 《Journal of Electronic Materials》1995,24(6):713-717
Valence band offsets at [100]-oriented heterojunctions between tensile-strained GaASj1−xPx and unstrained GaAs are studied experimentally and theoretically. Light-hole (LH) and heavy-hole (HH) offsets are first extracted
from the well-width dependence of valence subband splittings observed in luminescence spectra of tensile-strained GaAs1−xPx/GaAs quantum wells of various compositions (x = 0.06,0.09, and 0.19). This data is then combined with results from two other
laboratories, yielding a set of 30 independent experimental offset values for junctions with compositions throughout the range
0.06≤x ≤0.32. The data are found to be highly consistent, with linear fits δELH = −140x (meV) and δEHH= −401x (meV) describing the measured offsets to within less than 5 meV on average. Experimental results are then compared
with theoretical predictions for the GaAs1−x Px/GaAs system obtained from a tight-binding model for strained heterojunctions. Predictions from the tight-binding calculations
are found to lie within experimental scatter for the LH offsets, which define the valence band edge in these heterostructures,
while magnitudes of the tight-binding HH offsets exceed measured values by ~20% on average. 相似文献
2.
Daniel C. Bertolet Jung-Kuei Hsu Farid Agahi Kei May Lau 《Journal of Electronic Materials》1990,19(9):967-974
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/In0.11Ga0.89As, in which the QW layers are under biaxialcompression, and Al0.35Ga0.65As/GaAs0.82P0.18, 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. 相似文献
3.
S. Bürkner M. Maier E. C. Larkins W. Rothemund E. P. O’reilly J. D. Ralston 《Journal of Electronic Materials》1995,24(7):805-812
The dependence of the impurity-free interdiffusion process on the properties of the dielectric cap layer has been studied,
for both unstrained GaAs/AlxGa1−xAs and pseudomorphic Iny Ga1−yAs/GaAs MQW structures grown by molecular beam epitaxy. The influence of the cap layer thickness, composition, and deposition
technique on the degree of interdiffusion were all systematically investigated. Electron-beam evaporated SiO2 films of varying thickness, chemical-vapor-deposited SiOxNy films of varying composition, and spin-on SiO2 films were used as cap layers during rapid thermal annealing (850-950°C). Photoluminescence at 10K has been employed to determine
the interdiffusioninduced bandgap shifts and to calculate the corresponding Al-Ga and In-Ga interdiffusion coefficients. The
latter were found to increase with the cap layer thickness (e-beam SiO2) up to a limit determined by saturation of the outdiffused Ga concentration in the SiO2 caps. A maximum concentration of [Ga] = 4–7 ×1019 cm−3 in the SiO2 caps was determined using secondary ion mass spectroscopy profiling. Larger band-edge shifts are also obtained when the oxygen
content of SiOxNy cap layers is increased, although the differences are not sufficiently large for a laterally selective interdiffusion process
based on variations in cap layer composition alone. Much larger differences are obtained by using different deposition techniques
for the cap layers, indicating that the porosity of the cap layer is a much more important parameter than the film composition
for the realization of a laterally selective interdiffusion process. For the calculated In0.2Ga0.8As/GaAs interdiffusion coefficients, activation energies EA and prefactors Do were estimated to ranging from 3.04 to 4.74 eV and 5 × Kh−3 to 2 × 105 cm2/s, respectively, dependent on the cap layer deposition technique and the depth of the MQW from the sample surface. 相似文献
4.
We studied p-type GaAs/AIGaAs multiple quantum well (MQW) materials as a possible alternative to the current n-type GaAs/AIGaAs
MQWs for infrared detection. The advantage of p-type MQWs is that absorption of infrared radiation at normal incidence is
not selection rule forbidden as it is for the n-type. We have verified that significant photoresponse occurs at normal incidence
in p-type MQWs. We studied changes in the photoresponse spectrum as a function of well width and temperature. The MQW heterostructures
were designed to use bound to continuum intersubband absorption in the GaAs valence band and to have a peak photoresponse
near 8 μm. The photoresponse spectrum was compared to the first theoretical model of the bound to continuum absorption in
p-type GaAs/ AlGaAs MQWs. The theoretical absorption curve was found to be in good qualitative agreement with the experimental
results. 相似文献
5.
S. Moneger H. Qiang Fred H. Pollak T. F. Noble 《Journal of Electronic Materials》1995,24(10):1341-1344
Using contactless electroreflectance at 300 and 77K, we have studied the inter-subband transitions from a GaAlAs/InGaAs/GaAs/GaALAs
step quantum well structure (small well inside a large well) consisting of two layers A (InxGa1−xAs) and B (GaAs) with widths LA and LB, respectively, bounded by two thick barrier regions of Gax AlyAs. By comparison of the observed spectral features with an envelope function calculation, including the effects of strain,
we have been able to characterize the potential profile of the structure, i.e., LA, LB, x, and y. There is very good agreement between experiment and the intended materials param-eters. Such configurations are
of considerable importance since (a) they form the basis for pseudomorphic high electron mobility transistors, and (b) also
have applications in optoelectronics due to their large Stark shifts. 相似文献
6.
7.
We have theoretically studied the mobility limited by interface roughness scattering on two-dimensional electrons gas(2DEG) at a single heterointerface(triangle-shaped quantum well).Our results indicate that,like the interface roughness scattering in a square quantum well,the roughness scattering at the AlxGa1-xAs/GaAs heterointerface can be characterized by parameters of roughness height A and lateral A,and in addition by electric field F.A comparison of two mobilities limited by the interface roughness scattering between the present result and a square well in the same condition is given. 相似文献
8.
T. M. Cockerill D. V. Forbes H. Han B. A. Turkot J. A. Dantzig I. M. Robertson J. J. Coleman 《Journal of Electronic Materials》1994,23(2):115-119
Selective-area growth and regrowth using conventional atmospheric pressure metalorganic chemical vapor deposition is investigated for wavelength tuning in strained layer InxGa1-xAsGaAs-Aly Ga1-yAs quantum well lasers. Growth inhibition from a silicon dioxide mask is the mechanism used for the selective-area growth rate enhancement. By varying the width of the oxide stripe opening, differences in the growth rate yield different quantum well thicknesses, and hence different lasing wavelengths for devices on the same wafer. Both two-and three-step growth processes are utilized for selective-area epitaxy of strained layer InxGa1-xAs-GaAs quantum well active regions, with lasers successfully fabricated from the three-step growth. Scanning electron microscopy and transmission electron microscopy indicate that the absence of an oxide mask during AlyGa1-yAs growth is essential for successful device operation. A wide wavelength tuning range of over 630Å is achieved for lasers grown on the same substrate. 相似文献
9.
Low pressure metalorganic vapor phase epitaxy grown strained InGaAs/GaAs quantum well structures have been characterized by
photoluminescence and x-ray diffraction. It is shown that beyond the pseudomorphic limit, these structures show considerable
gallium/indium interdiffusion at the interfaces and partial strain relaxation in the quantum well layers. 相似文献
10.
JPR David R. Grey G. J. Rees A. S. Pabla T. E. Sale J. Woodhead J. L. Sanchez-Rojas M. A. Pate G. Hill P. N. Robson R. A. Hogg T. A. Fisher M. S. Skolnick D. M. Whittaker ARK Willcox D. J. Mowbray 《Journal of Electronic Materials》1994,23(9):975-982
High quality piezoelectric strained InGaAs/GaAs multi-quantum well structures on (111)B GaAs substrates have been grown by
solid-source molecular beam epitaxy in a PIN configuration. 10K photoluminescence (PL) shows narrow peaks with widths as low
as 3 meV for a 25-period structure while room temperature (RT) PL shows several higher order peaks, normally forbidden, indicating
breaking of inversion symmetry by the piezoelectric field. Furthermore, both the 10K PL peak position and the form of the
RT PL spectra depend on the number of quantum wells within the intrinsic region, suggesting that the electric-field distribution
is altered thereby. Diodes fabricated from these structures had sharp avalanche breakdown voltages (Vbd) and leakage currents as low as 8 × 10−6 A/cm2 at 0.95 Vbd, indicating quality as high as in (100) devices.
On leave from: Department de Ingeniera Electronica, Universidad Politecnica de Madrid, Madrid, Spain. 相似文献
11.
研究了GaAs/AlGaAs多量子阱(MQW)空间光调制器(SLM)在不同入射角度下的调制特性。对腔模位置与入射角度的关系进行了理论计算和实验验证,两者具有较好的一致性。当入射角在0°~75°之间变化时,腔模从871nm变化至845nm,可调节范围达26nm。当入射光从垂直入射变化为约45°入射时,SLM对比度从(CR)3.8提高到16.3,调制电压从9.5V下降至6.5V。理论分析和实验结果表明,入射角度调节能够有效提高GaAs/AlGaAs MQW SLM调制性能。 相似文献
12.
We studied the effects of Ar ion laser irradiation during the growth of InGaAs/ GaAs multiple quantum wells (MQW) structures
by metalorganic molecular beam epitaxy. Structural and optical properties were characterized by Nomarski microscopy, Dektak
stylus profiler, and low-temperature photoluminescence (PL) measurements. For MQW structures grown at a relatively low substrate
temperature (500°C), the laser irradiation influences greatly the growth process of the In^Ga^^As well and results in a large
blue shift of about 2000à in the PL peak. Such a large blue shift suggests that laser modification during growth could have
some novel applications in optoelectronics. On the other hand, the laser irradiation has relatively small effects on samples
grown at a higher substrate temperature (550°C). 相似文献
13.
Using MOVPE, we fabricated strained quantum well 1.3 μm lasers with an InGaP cladding layer on a GaAs substrate. The lasers had a high gain coefficient of 60 cm-1. Lasers with high reflection facets had a low threshold current density of 500 A/cm2, and a high characteristic temperature of 100 K 相似文献
14.
In this paper, we study the effect of the incorporation of nitrogen in strained GaInAs quantum well structures. We evaluate the influence of nitrogen on the conduction band energy by using the band anticrossing model. The incorporation of nitrogen appears to decrease the bandgap energy and increase the emission wavelength. The reduction of energy is due to the interaction of the energy of the conduction band with the level of nitrogen and more the concentration of nitrogen increases, more the energy of the band gap decreases. On the other hand, the emission wavelength increases, the advantage of the incorporation of nitrogen in such structures is to vary the wavelength between 0.980 and 1.3 μm while exploiting of course the composition of gallium, composition of nitrogen and the thickness of the quantum well. Less temperature insensitive devices are so intended to be fabricated. 相似文献
15.
We grew a 1.3 μm strained-layer quantum well (SL-QW) laser with InGaP cladding layers on a lattice-relaxation buffer layer
by metalorganic vapor phase epitaxy. For the lattice-relaxation buffer, we used a compositionally graded InGaAs/GaAs structure.
The significantly reduced surface roughness of the InGaP cladding layers achieved by supplying a large amount of H2Se enables CW operation of our 1.3 μm SL-QW laser. We achieved a low threshold current of less than 10 mA and a high characteristic
temperature of 100K around room temperature. 相似文献
16.
17.
S.J. Lade 《Microelectronics Journal》2004,35(5):401-410
Quantum well solar cells (QWSCs) are heterostructure devices intended to achieve higher efficiencies than conventional cells. This paper extends a previous model for QWSC current-voltage characteristics by revising the equations for the absorbed flux and by introducing expressions to calculate radiative recombination coefficients and well effective densities-of-states. This revised model is in agreement with previous experimental results for AlGaAs/GaAs. Since the revised model incorporates detailed balance calculations, its predictions are consistent with the efficiency restrictions of this theory. The revised model, however, does predict efficiency enhancements for QWSCs in some configurations if non-radiative recombination is dominant, even in such a poor QWSC material as AlGaAs/GaAs. 相似文献
18.
P. Kurpas A. Oster M. Weyers A. Rumberg K. Knorr W. Richter 《Journal of Electronic Materials》1997,26(10):1159-1163
Reflectance anisotropy spectroscopy (RAS) has been used to study As-by-P exchange during metalorganic vapor phase epitaxy.
The study focuses on the processes occurring during switching from GaAs to GaInP, especially the effect of purging PH3 over a GaAs surface. GaAsP/GaAs superlattices of different periodicity were grown and the P-content was determined by high-resolution
x-ray diffraction and correlated to the RAS spectra. From the temperature dependence of the P-content, an activation energy
of 0.56 eV was estimated for the incorporation mechanism. In addition to the insights into the processes at mixed group-V
heterointerfaces, our study demonstrates the reproducibility of RAS transients that thus can be used for process monitoring. 相似文献
19.
V. A. Wilkinson A. D. Prins D. J. Dunstan L. K. Howard M. T. Emeny 《Journal of Electronic Materials》1991,20(8):509-516
InxGa1-xAs quantum wells grown pseudomorphically in GaAs and AlGaAs with values ofx up to 0.25 have been studied by photoluminescence under high hydrostatic pressure. We concentrate here on the pressure range
where the emissions quench and take on the characteristics of theX-minima. In the InGaAs/GaAs structures, these transitions display an unexpected pressure coefficient, -2.6 meV/kbar, twice
that of theX minima in GaAs. We assign these transitions to theX minima in the wells, and therefore make a direct measurement of the strainedX positions as a function of composition. In the InGaAs/AIGaAs structures the crossovers occur against theX-minima in the barriers and these crossovers yield an accurate value for the band offset ratio for InGaAs/GaAs heterojunctions
which is found to be 60:40 (CB:VB). 相似文献
20.
J. Pamulapati P. K. Bhattacharya J. Singh P. R. Berger C. W. Snyder B. G. Orr R. L. Tober 《Journal of Electronic Materials》1996,25(3):479-483
We confirm that as the misfit strain in pseudomorphic epitaxial layer increases, surface thermodynamics controlled growth
modes can change from a layer-by-layer to a three-dimensional (3-D) island mode. Both in-situ reflection high energy electron
diffraction studies and in-situ scanning tunneling microscopy studies are utilized to demonstrate this transition to 3-D growth.
This concept allows one to grow GaAs/InxGa1-xAs/GaAs heterostructures where the electrons in InxGa1-xAs are possibly confined in lower dimensions. 相似文献