Dissolution and Growth of InGaSb Ternary Semiconductor under Microgravity

我们进行了不同类型的实验，以获得在微重力和地球上InGaSb三元半导体的溶解和生长信息。(1)中国返回式卫星上的微重力实验和地球上的参考实验。(a)空间处理样品的径向Ga成分分布均匀，界面基本平行；相反，土处理样品的上部区域含有较多的Ga成分，且溶解带向重力方向展宽。数值模拟结果表明，由于组分的差异，溶液和溶液/晶体界面中GaSb的组分分布受到溶质对流的显著影响；(b)与（111）A平面相比，（111）b平面溶入InSb的GaSb溶入量更大。(2)在飞机上进行的实验，结晶研究是在更低的重力水平（10^<-2>G）下进行的，使用飞机（以抛物线轨道飞行）和在地球上的正常重力条件下进行的。在失重作用下，InGaSb在结晶过程中形成了许多针状晶体。虽然形成了不同大小的针状晶体，但大多数晶体的尺寸都比较大。与此同时，在地球上结晶过程中产生的针状晶体与在失重条件下产生的晶体相比，尺寸要小得多。(a)在InGaSb结晶过程中，在样品表面观察到许多球形突起。由于InGaSb的液体密度大于固体密度，在InGaSb熔体结晶过程中出现了凸起。(b)观察到的突起与IML-2中in /GaSb/Sb的熔化和凝固实验中观察到的突起相似。微重力下形成的突起几乎是球形的，而正常重力下形成的突起不是完全球形的。由于地心引力的作用，投影的上表面趋于平坦。这表明重力对凸出物形成的影响。(c)结晶InGaSb的In组成随形成时的温度而变化。这符合InSb-GaSb三元相图。(4)温度梯度下的单向凝固(a)当晶种温度、加热速率、保温时间和冷却速率分别为648℃、20℃/min、40 h和0.5℃/min时，随着温度从1.3℃/cm增加到9.8℃/cm，组成比均匀的结晶部分长度变长。(b)随着冷却速率和初始In成分的减小，均匀In成分比下的晶体长度变长。(c)随着升温速率的增加，溶解面积减小。(d)溶解区域的形状取决于重力方向。对于水平炉，它们在重力方向上是垂直的，对于垂直炉和倾斜炉，它们在重力方向上展宽。(5)溶质输运随重力水平和g抖动的数值模拟。对溶液中的流动和成分分布进行了数值模拟，作为实验研究的分析支持。(a)在零重力条件下，由于没有流动，溶解的GaSb从界面向溶液中远离界面的区域扩散。这导致了溶液中沿轴向的成分梯度，但沿径向的Ga成分是均匀的。因此，GaSb的溶解在界面处均匀发生。这就产生了平面接口。相反，在正常重力作用下，Ga成分在径向上不均匀。从流线可以看出，在固液界面附近存在一个高速区。这是因为液态GaSb的密度（6.01 g/cm^3）比液态InSb的密度（6.32 g/cm^3）小，在浮力的作用下，大量富ga溶液向上部区域移动。这种浓度梯度成为界面处流动的驱动力。在固液界面处，由于溶液上部存在大量的Ga成分，抑制了上部区域GaSb的溶解。另一方面，在溶液的下部区域，存在大量的in组成。这增加了GaSb在溶液中的溶解，以满足二元InSb-GaSb相图。结果，固液界面的形状向底部变宽。这些数值结果可以定性地解释实验结果。(b)流矢量随着重力水平的减小而减小。随着重力水平的减小，界面的形状趋于平行。随着炉内升温速率的增大，溶出量减小。(c) g抖动对对流的影响随着频率的降低而增大。(d)在正常和零重力条件下，热马兰戈尼对流增强了自由表面附近的融化。在正常重力场下，由于重力偏析，溶质马兰戈尼对流对气流的贡献小于热态马兰戈尼对流。在零重力场下，热马兰戈尼对流和溶质马兰戈尼对流的存在对界面形状有很大影响。少

We have conducted different types of experiments to obtain information on dissolution and growth of InGaSb ternary semiconductor under microgravity and on earth.(1) The microgravity experiment performed in the Chinese recoverable satellite and the reference experiment on earth.(a) the Ga compositional profile of the space-processed sample was uniform in the radial direction, and the interfaces were almost parallel. On the contrary, the larger amount of Ga composition was incorporated in the upper region of the earth-processed sample, and the dissolved zone broadened towards gravitational direction. Numerical simulation results suggested that the GaSb compositional profile in the solution and solution/crystal interface was significantly affected by solutal convection due to compositional difference ; (b) the GaSb with the (111)B plane dissolved into the InSb melt much more than that with the (111)A plane.(2) Experiments performed using an airplane,Crystallization studies were done at a … More reduced gravity level of 10^<-2>G using an airplane (flying in a parabolic trajectory) and at normal gravity conditions on earth. During the crystallization of InGaSb under reduced gravity, there were many needle crystals formed. Though different sizes of these needle crystals formed, most of these crystals were relatively large sized. At the same time, most of the needle crystals resulted during the crystallization process done on earth were considerably smaller in size when compared with the crystals resulted in the reduced gravity condition.(3) Experiments using a drop tower,(a) During the crystallization of InGaSb, many spherical projections were observed on the surface of the sample. The projections emerged out during the crystallization of InGaSb from its melt due to the reason that the density of InGaSb liquid is larger than that of solid.(b) The observed projections were found to be similar to the projections observed in the melting and solidification experiment on In/GaSb/Sb done in IML-2. The projections formed under microgravity were almost spherical, whereas, the projection formed under normal gravity was not perfectly spherical. Due to gravitational pull, the top surface of the projection tended to become flat. This showed the influence of gravity on the formation of projections.(c) The In composition of the crystallized InGaSb varied depending on the existing temperature at the time of formation. This was in accordance with the InSb-GaSb ternary phase diagram.(4) Uni-directional solidification under a temperature gradient(a) When the Seed temperature, the heating rate, the holding period, and the cooling rate were fixed at 648 ℃, 20 ℃/min, 40 h, and 0.5 ℃/min, respectively, the length of the crystal portion with uniform In compositional ratio became longer as the temperature was increased from 1.3 ℃/cm to 9.8 ℃/cm.(b) The crystal length with uniform In compositional ratio became longer with the decrease of cooling rate and the initial In compositions.(c) The dissolved area decreased with the increase of heating rate.(d) The shapes of the dissolved region depend on the gravitational direction. They were perpendicular against the gravitational direction for the horizontal furnace, and broadened towards the gravitational direction in the case of the vertical furnace and the inclined furnace.(5) Numerical simulation on solute transportation as functions of gravity level and g-jitter.Numerical simulations on the flow and compositional distribution in the solution were performed as the analytical backup for the experimental studies.(a) Under zero gravity, as there is no flow, dissolved GaSb diffuses from the interface towards a region far from the interface in the solution. This brings about the compositional gradient along the axial direction in the solution, but the Ga composition is uniform along the radial direction. Therefore, the dissolution of GaSb takes place uniformly at the interface. This results in the flat interface. On the contrary, under normal gravity, the Ga composition is not homogeneous in the radial direction. From the stream lines, it can be understood that a high velocity region exists near the solid-liquid interface. This is because a large amount of Ga-rich solution moves to the upper region due to buoyancy as the density of liquid GaSb (6.01 g/cm^3) is smaller than that of liquid InSb (6.32 g/cm^3). This concentrational gradient becomes a driving force of flow at the interface. At the solid-liquid interface, the dissolution of GaSb in the upper region is suppressed as large amount of Ga composition exists in the upper region of the solution. On the other hand, in the lower region of the solution, a large amount of In composition exists. This increases the dissolution of GaSb into the solution to satisfy the binary InSb-GaSb phase diagram. As a result, the shape of solid-liquid interface broadens towards the bottom. These numerical results can qualitatively explain the experimental results.(b) The flow vector becomes smaller as the gravity level decreases. The shape of the interface becomes parallel with the decrease of gravity levels. With the increase of heating rate in the furnace, the dissolved amount decreases.(c) The effect of g-jitter on the convection increases as the frequency decreases.(d) Thermal Marangoni convection enhances the melting near the free surface under both normal and zero gravity conditions. Under the normal gravity field, the contribution of the solutal Marangoni convection to the flow is less than that of the thermal Marangoni convection because of gravitational segregation. Under zero gravity filed, the inteface shape is greatly affected by both the presence of thermal and solutal Marangoni convections. Less