共查询到20条相似文献,搜索用时 890 毫秒
1.
L. H. Zhang S. D. Pearson W. Tong B. K. Wagner J. D. Benson C. J. Summers 《Journal of Electronic Materials》1998,27(6):600-604
This paper presents a study of both as-grown and annealed p-type Hg1−xCdxTe layers that were doped using a cadmium arsenide source. It is shown that by using a metalorganic molecular beam epitaxy
system stable and reproducible p-type HgCdTe:As layers were obtained through direct homogeneous doping. The hole concentrations
in the as-grown and annealed samples were 8 × 1016 to 3 × 1017 cm−3 with mobilities of 120∼300 cm2/V-s. The as-grown HgCdTe:As layers had very good crystalline quality with double crystal x-ray rocking curve line-widths
ranging from 27 to 42 arc sec. Experimental data demonstrated a strong correlation of hole concentration and mobility with
the surface morphology and crystalline quality as a function of Hg flux. The optimum growth window was defined by a narrow
range of Hg flux values that gave a smooth film with fewer voids, and higher hole concentrations and mobilities than were
obtained at lower or higher Hg fluxes. This correlation between the growth window defined by the surface morphology and the
dopant behavior was very important for the successful growth of p-type As-doped HgCdTe materials. 相似文献
2.
Lijie Zhao J. S. Speck R. Rajavel J. Jensen D. Leonard T. Strand W. Hamilton 《Journal of Electronic Materials》2000,29(6):732-735
Transmission electron microscopy (TEM) was used to evaluate the microstructure of molecular beam epitaxy (MBE) grown (211)B
oriented HgCdTe films. TEM analysis of in-situ doped p-on-n and n-p-n device structures will be presented. Under fully optimized
growth conditions the substrate-epilayer interface is free of threading dislocations and twins, and a high degree of structural
integrity is retained throughout the entire device structure. However, under non-optimal growth conditions that employ high
Hg/Te flux ratios, twins can be generated in the p-type layer of p-on-n device structure, resulting in roughness and facetting
of the film surface. We propose a mechanism for twin formation that is associated with surface facetting. TEM evaluation of
voids, threading dislocations and Te-precipitates in HgCdTe films are also discussed. 相似文献
3.
Molecular beam epitaxy HgCdTe growth-induced void defects and their effect on infrared photodiodes 总被引:3,自引:0,他引:3
J. M. Arias M. Zandian J. Bajaj J. G. Pasko L. O. Bubulac S. H. Shin R. E. De Wames 《Journal of Electronic Materials》1995,24(5):521-524
We have carried out a study and identified that MBE HgCdTe growth-induced void defects are detrimental to long wavelength
infrared photodiode performance. These defects were induced during nucleation by having surface growth conditions deficient
in Hg. Precise control and reproducibility of the CdZnTe surface temperature and beam fluxes are required to minimize such
defects. Device quality material with void defect concentration values in the low 102 cm2 range were demonstrated. 相似文献
4.
HgCdTe是一种有广泛应用前景的半导体光电材料。从投资上看,它已成为仅次于Si和GaAs的第三种最重要的半导体。本文系统地介绍了HgCdTe材料的基本性质及HgCdTe的晶体生长,对液相外延生长HgCdTe晶体的理论和工艺问题作了较详细的论述。 相似文献
5.
J. Zhao Y. Chang G. Badano S. Sivananthan J. Markunas S. Lewis J. H. Dinan P. S. Wijewarnasuriya Y. Chen G. Brill N. Dhar 《Journal of Electronic Materials》2004,33(8):881-885
We present results on the surface morphology and recombination lifetimes of molecular-beam epitaxy (MBE)-grown HgCdTe (211)B
epilayers and correlate them with the roughness of the CdZnTe substrate surfaces. The substrate surface quality was monitored
by in-situ spectroscopic ellipsometry (SE) and reflection high-energy electron diffraction (RHEED). The SE roughness of the
substrate was measured after oxide desorption in the growth chamber. The RHEED patterns collected show a strong correlation
with the SE roughness. This proves that SE is a valuable CdZnTe prescreening tool. We also found a correlation between the
substrate roughness and the epilayer morphologies. They are characterized by a high density of thin elongated defects, “needle
defects,” which appear on most samples regardless of growth conditions. The HgCdTe epilayers grown on these substrates were
characterized by temperature-dependent, photoconductive decay-lifetime data. Fits to the data indicate the presence of mid-gap
recombination centers, which were not removed by 250°C/24-h annealing under a Hg-rich atmosphere. These centers are believed
to originate from bulk defects rather than Hg vacancies. We show that Te annealing and CdTe growth on the CdZnTe substrates
smooth the surface and lower substantially the density of needle defects. Additionally, a variety of interfacial layers were
also introduced to reduce the defect density and improve the overall quality of the epilayer, even in the presence of less
than perfect substrates. Both the perfection of the substrate surface and that of its crystalline structure are essential
for the growth of high-quality material. Thus, CdZnTe surface polishing procedures and growth techniques are crucial issues. 相似文献
6.
As在HgCdTe分子束外延中的表面粘附系数 总被引:5,自引:1,他引:4
报道了用二次离子质谱分析 (SIMS)方法对As在碲镉汞分子束外延中的掺入行为的研究结果 .发现As在CdTe、HgCdTe表面的粘附系数很低 ,并与Hg的介入密切相关 .对于单晶HgCdTe外延 ,在 170℃生长温度下As的粘附率相对于多晶室温淀积仅为 3× 10 -4,在此生长温度下 ,通过优化生长条件获得了表面形貌良好的外延材料 .通过控制As束源炉的温度可以很好地控制As在HgCdTe层中的原子浓度 . 相似文献
7.
Surface Morphology and Defect Formation Mechanisms for HgCdTe (211)B Grown by Molecular Beam Epitaxy 总被引:1,自引:0,他引:1
Yong Chang C.R. Becker C.H. Grein J. Zhao C. Fulk T. Casselman R. Kiran X.J. Wang E. Robinson S.Y. An S. Mallick S. Sivananthan T. Aoki C.Z. Wang D.J. Smith S. Velicu J. Zhao J. Crocco Y. Chen G. Brill P.S. Wijewarnasuriya N. Dhar R. Sporken V. Nathan 《Journal of Electronic Materials》2008,37(9):1171-1183
The surface morphology and crystallinity of HgCdTe films grown by molecular beam epitaxy (MBE) on both CdZnTe and CdTe/Si
(211)B substrates were characterized using atomic force microscopy (AFM), as well as scanning (SEM) and transmission (TEM)
electron microscopy. Crosshatch patterns and sandy-beach-like morphologies were commonly found on MBE (211) HgCdTe epilayers
grown on both CdZnTe and CdTe/Si substrates. The patterns were oriented along the , , and directions, which were associated with the intersection between the (211) growth plane and each of the eight equivalent HgCdTe
slip planes. This was caused by strain-driven operation of slip in these systems with relative large Schmid factor, and was
accompanied by dislocation formation as well as surface strain relief. Surface crater defects were associated with relatively
high growth temperature and/or low Hg flux, whereas microtwins were associated with relatively low growth temperature and/or
high Hg flux. AFM and electron microscopy were used to reveal the formation mechanisms of these defects. HgCdTe/HgCdTe superlattices
with layer composition differences of less than 2% were grown by MBE on CdZnTe substrates in order to clarify the formation
mechanisms of void defects. The micrographs directly revealed the spiral nature of growth, hence demonstrating that the formation
of void defects could be associated with the Burton, Cabrera, and Frank (BCF) growth mode. Void defects, including microvoids
and craters, were caused by screw defect clusters, which could be triggered by Te precipitates, impurities, dust, other contamination
or flakes. Needle defects originated from screw defect clusters linearly aligned along the directions with opposite Burgers vector directions. They were visible in HgCdTe epilayers grown on interfacial superlattices.
Hillocks were generated owing to twin growth of void or needle defects on (111) planes due to low growth temperature and the
corresponding insufficient Hg movement on the growth surface. Therefore, in addition to nucleation and growth of HgCdTe in
the normal two-dimensional layer growth mode, the BCF growth mode played an important role and should be taken into account
during investigation of HgCdTe MBE growth mechanisms. 相似文献
8.
Physical structure of molecular-beam epitaxy growth defects in HgCdTe and their impact on two-color detector performance 总被引:1,自引:0,他引:1
A. A. Buell L. T. Pham M. D. Newton G. M. Venzor E. M. Norton E. P. Smith J. B. Varesi V. B. Harper S. M. Johnson R. A. Coussa T. De Leon J. A. Roth J. E. Jensen 《Journal of Electronic Materials》2004,33(6):662-666
The flexible nature of molecular-beam epitaxy (MBE) growth is beneficial for HgCdTe infrared-detector design and allows for
tailored growths at lower costs and larger focal-plane array (FPA) formats. Control of growth dynamics gives the MBE process
a distinct advantage in the production of multicolor devices, although opportunities for device improvement still exist. Growth
defects can inhibit pixel performance and reduce the operability in FPAs, so it is important to understand and evaluate their
properties and impact on detector performance. The object of this paper is to understand and correlate the effects of macrodefects
on two-color detector performance. We observed the location of single-crystal and polycrystalline regions on planar and cross-sectioned
surfaces of two-color device structures when void defects were viewed by scanning electron microscopy (SEM). Compositional
analysis via energy dispersive x-ray analysis (EDXA) of voids in the cross section showed elevated Te and reduced Hg when
compared to defect-free growth areas. The second portion of this study examined the correlation of macrodefects with pixel
operability and diode current-voltage (I–V) characteristics in mid-wavelength infrared (MWIR)/MWIR (M/M) and long wavelength
infrared (LWIR)/LWIR (L/L) two-color devices. The probability of diode failure when a void is present is 98% for M/M and 100%
for L/L. Voids in two-color detectors also impact diodes neighboring their location; the impact is higher for L/L detectors
than M/M detectors. All void-containing diodes showed early breakdown in the I–V characteristics in one or both bands. High
dislocation densities were observed surrounding voids; the high density spread further from the void for L/L detectors compared
to M/M detectors. 相似文献
9.
J.D. Benson L.A. Almeida M.W. Carmody D.D. Edwall J.K. Markunas R.N. Jacobs M. Martinka U. Lee 《Journal of Electronic Materials》2007,36(8):949-957
The as-grown molecular beam epitaxy (MBE) (211)B HgCdTe surface has variable surface topography, which is primarily dependent on substrate temperature and substrate/epilayer mismatch. Nano-ripple formation and cross-hatch patterning are the predominant structural features observed. Nano-ripples preferentially form parallel to the \( [\bar {1}11] \) and are from 0 Å to 100 Å in height with a wavelength between 0.1 μm and 0.8 μm. Cross-hatch patterns result from slip dislocations in the three {111} planes intersecting the (211) growth surface. The cross-hatch step height is 4 ± 1 Å (limited data set). This indicates that only a bi-layer slip (Hg/Cd + Te) in the {111} slip plane occurs. For the deposition of MBE (211)B HgCdTe/CdTe/Si, the reorientation of multiple nano-ripples coalesced into “packets” forms cross-hatch patterns. The as-grown MBE (211)B CdTe/Si surface is highly variable but displays nano-ripples and no cross-hatch pattern. Three types of defects were observed by atomic force microscopy (AFM): needle, void/hillock, and voids. 相似文献
10.
研究了利用GaAs作为衬底的HgCdTe MBE薄膜的表面缺陷,发现其中一类缺陷与Hg源中杂质有关。采用SEM对这类缺陷进行正面和横截面的观察,并采用EDX对其正面和横截面进行成分分析。并设计了两个实验:其一,在CdTe/GaAs衬底上,低温下用Hg源照射20min,再在其上继续高温生长CdTe;其二,在CdTe/GaAs衬底上,一直用Hg源照射下高温生长CdTe。两个实验后CdTe表面都出现与HgCdTe表面相比在形状和分布上类似的表面缺陷,采用光学显微镜和SEM对CdTe表面缺陷进行了观察,通过CdTe表面缺陷和HgCdTe表面缺陷的比较,我们证实了这类表面缺陷的成核起源于Hg源中杂质。 相似文献
11.
T. Aoki Y. Chang G. Badano J. Zhao C. Grein S. Sivananthan David J. Smith 《Journal of Electronic Materials》2003,32(7):703-709
Surface-void defects observed in Hg1−xCdxTe (x ∼ 0.2–0.4) alloys grown by molecular-beam epitaxy (MBE) have been investigated using scanning and high-resolution transmission-electron
microscopy (HRTEM) as well as atomic force microscopy (AFM). These surface craters, which have been attributed to Hg-deficient
growth conditions, were found to originate primarily within the HgCdTe epilayer, rather than at the CdZnTe substrate, and
they were associated with the local development of polycrystalline morphology. High-resolution observations established the
occurrence of finely spaced HgCdTe/Te intergrowths with semicoherent and incoherent grain boundaries, as well as small HgCdTe
inclusions embedded within the Te grains. This study is the first time that high-resolution electron microscopy has been used
to investigate this type of defect. 相似文献
12.
采用含水硫化的方法对p型HgCdTe材料进行了表面钝化。XPS分析结果表明,Hg0.734Cd0.266Te表面形成了CdS薄膜,膜层里含有少量的Te和Hg不含氧。 相似文献
13.
14.
研究了HgCdTe液相外延薄膜表面两类宏观缺陷的形成原因.研究表明,大部分表面凹陷点(void)缺陷的形成是由衬底的蜡沾污所引入的,而表面凸起点(hill-like)是由衬底边缘脱落的CdZnTe微颗粒造成的,通过控制外延生长前的衬底处理过程,可以抑制这两类缺陷,从而生长出零(宏观)缺陷密度的优质HgCdTe外延薄膜. 相似文献
15.
Optimization of the structural properties of Hg1−x CdxTe (x = 0.18−0.30) alloys: Growth and modeling
A. Parikh S. D. Pearson R. N. Bicknell-Tassius L. H. Zhang R. Benz C. J. Summers 《Journal of Electronic Materials》1997,26(6):524-528
The conditions for the metalorganic molecular beam epitaxial growth of Hg1−xCdxTe (x = 0.18−0.32) alloys at very low growth temperatures (T ≤150°C) have been optimized by correlating the surface properties
and crystalline perfection with the incident Hg flux. A window for growth has been defined for x = 0.18, 0.23, and 0.32. A
thermodynamic model has been developed to account for void formation. A neural net model has been used for the first time
to model the dependence of void density on the Hg flux and the x-ray rocking curve widths on growth parameters. The combination
of these two complementary modeling techniques allows for a flexible process optimization to be carried out with a minimum
effort spent in calibration runs. 相似文献
16.
E. C. Piquette M. Zandian D. D. Edwall J. M. Arias 《Journal of Electronic Materials》2001,30(6):627-631
A semi-empirical constraint to the thermodynamical model for growth of Hg1−xCdxTe (MCT) by molecular beam epitaxy is described. This constraint, derived by forcing the population of Hg atoms in a surface
layer to be proportional to the HgTe fractional growth rate, can determine an optimal total growth rate for specific beam
fluxes and substrate temperature. Utilizing improved growth conditions determined by this model has resulted in MCT layers
with consistently lower visible defect density (e.g., voids). The majority of recent layers grown using the constrained conditions
has achieved defect densities limited by the CdZnTe substrate. On the highest quality substrates, total defect densities have
consistently been reduced to the 100–200 cm−2 range using the improved conditions for compositions x=0.2 to x=0.6. On more typical substrates, the total defect density
is 1000–1500 cm−2. This compares with densities of 3000–5000+ cm−2 for old layers grown under non-optimized conditions. The density of voids has remained about the same upon using the improved
conditions, and is determined primarily by the Te precipitate content of the substrate, but microdefect (hillock) density
has been reduced by almost a factor of ten. 相似文献
17.
R. Haakenaasen E. Selvig C. R. Tonheim K. O. Kongshaug T. Lorentzen L. Trosdahl-Iversen J. B. Andersen P. Gundersen 《Journal of Electronic Materials》2010,39(7):893-902
This paper presents results from recent work on molecular beam epitaxy growth of HgCdTe at the Norwegian Defence Research
Establishment (FFI), including studies of material properties and fabrication of photodiodes and nanostructures. Systematic
studies of defect morphology in HgTe and Hg1−x
Cd
x
Te have revealed that there is a minimum in the area covered by defects just below the onset of Te precipitation. The shape
and density of microvoids in HgTe can be used to determine the deviation from the optimal growth temperature. This can be
further related to the optimal growth temperature of Hg1−x
Cd
x
Te with any Cd mole fraction by thermodynamic calculations. A mechanism for the formation of microvoids and needles has been
presented. Photoluminescence (PL) has been used to study layers without doping and with Hg vacancy, Ag, and In doping. Planar
photodiodes with high dynamic resistance and good quantum efficiency were fabricated by ion-milling vacancy-doped mid-wave
and long-wave infrared layers. Quantum wells (QWs) with good crystallinity and high PL light output have been grown. Surface
patterning has been found to enhance light emission from HgCdTe thin-film and QW samples by ∼30%. Single-crystal HgTe and
segmented HgTe/Te nanowires have been grown, and the resistivity of the nanowires has been measured by conductive atomic force
microscopy (AFM), where the AFM tip has been used as a mobile electrode. 相似文献
18.
生长功率对HgCdTe薄膜微观结构以及表面形貌影响 总被引:1,自引:0,他引:1
实验采用射频磁控溅射生长了HgCdTe薄膜,并利用台阶仪、XRD、原子力显微镜等现代分析手段对HgCdTe薄膜的生长速率、物相、表面形貌进行了研究。实验结果表明,随着溅射功率增大,其生长速率成线性增大,当溅射功率低于30w时,薄膜XRD衍射图谱上没有出现任何特征衍射峰,只是在2θ=23°附近出现衍射波包,材料具有明显的非晶态特征,当溅射功率高于30w时,XRD表现为多晶结构;AFM和SEM分析表明生长速率对HgCdTe薄膜表面粗糙度、形貌、形成机理等有直接影响,随着生长速率提高,薄膜表面粗糙度逐渐增大,且薄膜逐渐形成“迷津”结构。 相似文献
19.
为了研究液相外延碲镉汞薄膜表面缺陷形成机制,采用光刻工艺结合化学腐蚀方法在碲锌镉衬底表面实现了网格化,研究了碲锌镉近表面富碲沉积相与外延薄膜表面缺陷的关系.结果表明:衬底近表面富碲沉积相会导致碲镉汞薄膜表面孔洞、类针形凹陷坑缺陷以及三角形凹陷坑聚集区;在液相外延过程中,高温碲镉汞熔液与CdZnTe衬底间的回熔作用可以减少与富碲沉积相相关的表面缺陷,薄膜表面缺陷与衬底表面富碲沉积相的匹配度与回熔深度负相关;回熔过程以及富碲沉积相形态、深度影响HgCdTe薄膜表面缺陷形态和分布. 相似文献
20.
Wang Guanghua Kong Jincheng Li Xiongjun Qiu Fen Li Cong Yang Lili Kong Lingde Ji Rongbin 《半导体学报》2010,31(5)
Mercury cadmium telluride films were grown by the RF magnetron sputtering technique at different sputtering powers.In experiment,X-ray diffraction (XRD) and atomic force microscopy (AFM) have been used to characterize the microstructure of HgCdTe films.The experimental results showed that when the growth power increased,the growth rate of HgCdTe films increased; when the growth power was less than 30 W,the HgCdTe film deposited by RF magnetron sputtering was amorphous; when the growth power was more than 30 W,the films exhibited polycrystalline structure.Films deposited at different growth rates were found to have characteristically different formations and surface morphologies; as observed through AFM,the surface morphology is composed of longitudinal islands forming a maze-like pattern in the high deposition rate.AFM analysis also illustrated that a significant reduction in the areal density of large islands and characteristically smoother films was achieved using a low deposition rate. 相似文献