GaAs[100]衬底的择优腐蚀

(一)引言 GaAs是闪锌矿结构,在[111]方向有极性,当选择适当的择优腐蚀液时,各晶面的腐蚀速度有[110]≥B[111]≥[100]>A[111]关系。A[111]面是难以被腐蚀的。因此,它对腐蚀图形起重要作用,利用这个特点可以设计和制造各种形状的新器件。本文介绍了     

GaAs、GaAlAs晶片的化学择优腐蚀

本文在总结实验的基础上,给出了化学腐蚀的选择原则。并针对化学腐蚀中较重要的晶向择优和异质择优腐蚀,借助大量的曲线和照片,就 GaAs、GaAlAs材料做了讨论。最后,简单介绍了一下它们的应用。     

用择优腐蚀技术制作MMI型GaAs光功率分配器

通过对器件结构进行优化设计和择优腐蚀技术 ,用 H3 PO4 - H2 O2 - H2 O系腐蚀液制作了能直接与单模光纤阵列相耦合的 MMI型 Ga As1× 4光功率分配器 .最后用 1 .3 μm波长的He- Ne激光进行了测试 ,发现该器件基本实现了功率均分要求 ,功率离散度为 0 .1 55d B.     

GaAs的气相腐蚀

在GaAs气相生长时,有的情况下能够在衬底与生长层的界面处形成高阻层,这是制备GaAs的器件中的问题所在。自从沃耳夫报导采用气相腐蚀可有效地除去这种高阻层以来,在生长开始前,一般都进行气相腐蚀。可是关于GaAs的气相腐蚀,在生长机构的分析方面有许多的报导,而从表面处理角度写出的报告却很少。作为外延生长前的处理,气相腐蚀的必要条件是:(1)腐蚀后能够保持镜面状态,(2)腐蚀-生长变换必须连续地并迅速地进行。前者作为外延生长前的处理是当然的。因为生长中     

用于GaAs的新腐蚀液的腐蚀特性和动力学

系统地研究了新的GaAs腐蚀液HCl-H_2O_2-H_2O.用它腐蚀的GaAs表面具有的残留氧化物膜较薄,且不易引起杂质沾污.给出了等腐蚀速率的三元图和各区中的激活能.研究了对于GaAs及常用于GaAs器件工艺中之金属的各种腐蚀特性以及对于器件工艺中常用的各种光刻胶的溶解性,并与其他腐蚀液系统作了对比.实验表明,腐蚀是依照氧化随后溶解氧化物的过程进行的.考虑到溶液中组分间的化学反应 pA+qB→产物,提出了一般的腐蚀速率方程.用于HCl-H_2O_2-H_2O系统的计算结果与实验数据一致.     

TMG和TEGMOCVD生长GaAs物理化学研究

本文采用三甲基镓和三乙基镓为镓源的金属有机化合物气相沉积，获得了高质量的ＧａＡｓ外延层，生长速率随ＴＭＧ和ＴＥＧ的浓度增加而增高和理论计算基本相符，而与ＡｓＨｓ浓度无关，用自制的ＴＥＧ为镓源生长的ＧａＡｓ有较高的迁移率。     

光子辅助GaAs的干法腐蚀

业已用氟化氩激光的紫外线辐射完成了单晶砷化镓的大面积腐蚀。该工艺以甲基或三氟甲基与溴基的光化学反应为基础。具有各向异性腐蚀的特点,已腐蚀出小于1μ的线条。     

GaAs和InP基HFET工艺中的选择腐蚀

综合了ＧａＡｓ和ＩｎＰ基ＨＦＥＴ工艺中选择腐蚀技术的有关报道,重点介绍了应用ＩＣＰ设备和气体组合ＢＣＩ＋ＳＦ６进行异质结材料组合的干法腐蚀实验,腐蚀后在显微镜和扫描电镜窗口平整干净、作迁移率测试等为法腐蚀的片子相比较没有看出差别,适宜用于器件工艺。     

Selective epitaxial growth of GaAs from the liquid phase

The epitaxial growth technique from the liquid phase using the selective windows was applied to GaAs. The overgrowth phenomenon as well as the change of the window shape and its orientation can be eliminated by properly choosing the growth conditions. Here are discussed the factors influencing these conditions. Good quality mono- and double-layer structures were obtained. It was established that selective liquid phase epitaxy can be applied with success in GaAs planar technology.     

Selective growth of GaAs and GaAlAs by Cl-assisted OMVPE at atmospheric pressure

Selective epitaxy of GaAs is generally obtained at low pressure, when the diffusion length of the active species over the dielectric mask is large enough. Another way is to use an organochloride as a precursor, which suppresses the deposition over the dielectric. This method is also used at reduced pressure. In this work, we have obtained selective area epitaxy of GaAs and GaAIAs for a wide range of aluminium composition by adding a controlled flow of AsCl₃ during a conventional OMVPE growth at atmospheric pressure. This method is called Cl-assisted OMVPE. When no AsCl₃ is used, a finely structured polycrystal is deposited on the mask. When AsCl₃ is introduced into the reactor, with otherwise the same growth conditions, complete selectivity was obtained over a 100μm wide Si₃N₄ mask. We have studied the influence of the growth temperature, the TMG/ AsCl₃ and the AsH₃/TMG ratios on the growth selectivity. We have also studied the evolution of the limiting planes of the selectively grown ridges with different growth conditions. Finally, on a selectively grown GaAs/GaAlAs double heterostructure, room temperature photoluminescence topography was performed.     

GaAs衬底层选择性腐蚀技术

本文在ＧａＡｓＧａＡｌＡｓ选择性腐蚀的基础上进行了腐蚀ＧａＡｓ衬底层获得ＧａＡ／ＧａＡｌＡｓ外延层薄膜的二次腐蚀技术。最终选用了Ｃ３Ｈ４（ＯＨ）（ＣＯＯＨ）３．Ｈ２Ｏ－Ｈ２Ｏ２系选择性腐蚀液和Ｈ２ＳＯ４－Ｈ２Ｏ２系腐蚀液，获得了快速，可控制，重复性好的可全部可局部去除衬底的腐蚀方法。     

Selective growth of CdTe on Si and GaAs substrates using metalorganic vapor phase epitaxy

Epitaxial lateral overgrowth (ELO) is a new technique to grow low-defect-density thin films on lattice-mismatched substrates. For the ELO growth of CdTe and HgCdTe on Si substrate to be successful, the first requirement is that the growth should be selective. To that end, we have used several mask materials, and several growth conditions in order to obtain selective growth. A number of growth-experiments have been carried out, with temperatures in the range from 380°C to 550°C, and pressures in the range from 380 torr to less than 20 torr. Perfectly selective growth of CdTe has been achieved on Si and GaAs substrates using Si₃N₄ as the mask layer. Successful lateral epitaxial growth of CdTe was also achieved.     

Selective area growth of GaAs with semiconductor-metal-semiconductor structures using pulsed-mode operation of MOCVD

Selective area growth of GaAs with semiconductor-metal-semiconductor structures using pulsed-mode operation of MOCVD, which controls the flow of trymethylgallium (TMG) at regular intervals, is reported. GaAs is selectively grown over tungsten gratings on (100) GaAs substrates. Tungsten gratings are masked with SiO₂ for the selective growth and it is possible to have good GaAs growth over W gratings without keeping the substrate temperature high and the growth rate low. The ideality factor and the barrier height of the W-GaAs Schottky diode in-situ annealed under the growth conditions show slight degradation with increased growth time. Using double crystal x-ray diffractometer and Auger electron spectroscopy analysis, it is shown that the interdiffusion of W and GaAs takes place. A vertical FET is fabricated to show the device application of this selective growth method.     

Growth condition dependence for GaAs selective epitaxial growth by molecular beam epitaxy

GaAs selective epitaxial growth by conventional molecular beam epitaxy (MBE) was studied while varying its growth conditions, such as substrate temperature. As pressure, growth rate, and Si or Be doping. Selectivity is improved with the increase in substrate temperature, and with the decrease in As pressure or growth rate. Si and Be were doped up to 3 x 10¹⁸ and 3 × 10¹⁹ cm⁻³, respectively. While no Si doping influence was observed, Be doping degraded the surface morphology. Selective epitaxial growth by conventional MBE with appropriate growth conditions will be applicable to device fabrication.     

Hole traps in bulk and epitaxial GaAs crystals

Twelve different hole traps have been characterised in v.p.e., 1.p.e., m.b.e. and bulk-grown GaAs from d.1.t.s. experiments. Most are related to the presence of different impurities, some of which are identified. Although far from complete, this catalogue of hole traps can be a working tool, particularly for the assessment of the impurity contamination in a material.     

Selective area epitaxy of GaAs using tri-isopropylgallium

We have studied the selective area epitaxy of GaAs by chemical beam epitaxy, using tri-isopropylgallium as the Ga source. The results show that GaAs can be selectively grown at a rate of up to ∼0.36 μm/h on patterned GaAs substrates at temperatures as low as 380°C. A low selective growth temperature allows us to utilize deep-ultraviolet radiation to modify the GaAs surface oxides for use as the masking material. We found that excess AsH₃ over-pressure degrades the selectivity significantly, and the maximum selective growth thickness is limited by a critical total adatom coverage on the mask. In addition, the low selective growth temperature does not result in a very high C background concentration. Initial Hall measurements indicate that unintentional C doping levels are at least two orders of magnitude lower than those in GaAs layers grown under comparable conditions using trimethylgallium.     

“Exciton” photoconductivity in GaAs crystals

The spectral dependence of the photoconductivity in epitaxial GaAs of high purity and crystalline perfection grown on a semiinsulating GaAs substrate are measured at 1.7 and 77 K and analyzed theoretically. The developed theory of photoconductivity spectra takes into consideration the analytical shape of the exciton absorption edge in semiconductor crystals, the transport of photogenerated charge carriers, the finite thickness of the crystal, and the presence of surface recombination centers. It is shown that, when the excitation photon energy is lower than the band gap, the photoconductivity spectrum is determined by elementary excitations of the exciton type, while at higher excitation energies the spectrum is determined by surface states as well as by processes associated with optical-phonon emission. It is found that, in the samples under study, the probability of the direct formation of excitons upon the absorption of light can be comparable to the probability of their formation from a thermalized electron-hole gas.