【作者】 汤亮亮；

【导师】 林其钊； 叶宏；

【作者基本信息】 中国科学技术大学 ， 工程热物理， 2014， 博士

【摘要】 锌(Zn)是一种P型掺杂物质,其气相扩散过程可广泛应用于Ⅲ-Ⅴ族化合物半导体(GaSb、GaAs、GaP、InAs等)的P型掺杂工艺,因此研究Zn在上述材料中的扩散规律对器件制造有重要帮助。然而在恒定表面Zn浓度的扩散情况下,Zn在Ⅲ-Ⅴ族化合物半导体中的扩散曲线并不遵循余误差函数分布,而是呈现出具有双重扩散前沿的kink-and-tail形貌或单扩散前沿的box形貌。我们研究了Zn在GaSb、GaAs和InAs这三种材料中的扩散规律。对于Zn在GaSb中的扩散,我们发现在扩散源中加入Ga元素可以遏制Zn扩散曲线中表面高浓度区域的产生,从而使Zn扩散曲线从kink-and-tail类型向box类型转换;kink-and-tail曲线中以kink点为界限划分出的表层与尾部区域都具有良好的生成规律,表层区域扩散率(D)与Zn浓度(C)的平方成正比,即D∝C2,尾部区域则有D∝C;box类型曲线的生成规律与kink-and-tail曲线尾部的生成规律是相同的,光致发光(PL)分析表明它们都具有代表Ga原子过剩的PL峰,证实了Zn在这两个区域都是通过踢出晶格中Ga原子的kick-out方式进行扩散的。Zn在GaAs中的扩散机理与在GaSb中的非常相似,而在InAs中的扩散机理却有较大差别。无论是采用纯Zn或者Zn-In合金作为扩散源,Zn在InAs中都生成box类型扩散曲线,其中以Zn-In合金作为扩散源生成的box曲线完全符合D∝C的关系,不会出现其它box曲线中极浅层区域存在的D∝C-2的现象。基于扩散源中Ga原子可遏制Zn在GaSb中表面高浓度区域产生的发现,我们提出了采用Zn-Ga合金扩散源的密封式扩散法来制备GaSb红外电池。传统GaSb电池制备工艺都是采用以Zn-Sb合金作为扩散源的准密封式扩散法制备PN结,生成的是具有表面高浓度扩散区域的kink-and-tail类型Zn曲线,需要将kink点之前的区域精确腐蚀掉以提高量子效率,然而对此百纳米级区域进行精确腐蚀是非常困难的。我们采用Zn-Ga合金扩散源的密封式扩散法直接生成box类型曲线,并制备了GaSb红外电池。该方法简化了电池制备工艺,并且可以保持不同批次的电池电学输出性能稳定,有利于批量制备。更多还原

【Abstract】 Zinc is a p-type dopant for semiconductors, zinc vapor phase diffusion process can be widely used for the P-type doping of III-V compound semicondutors such as GaSb, GaAs, GaP, InAs, etc. Therefore the investigation on the behavior of zinc diffusion in the above materials are important for device fabrication. However, zinc profiles in III-V compound semicondutors do not follow the complementary-error-function under the constant zinc surface concentration. Zinc profiles will show the kink-and-tail shapes with two diffusion fronts or the box shapes with a single diffusion front.We investigated the behaviors of zinc diffuion in GaSb, GaAs and InAs. For zinc diffusion in GaSb, we found that Ga atoms from diffusion sources suppressed the formation of the high-concentration surface diffusion regions in zinc profiles, thus converting the kink-and-tail-shaped profile into the box-shaped profile; our analysis demonstrated that both the surface and tail regions in the kink-and-tail profiles showed good regularities, the zinc diffusion coefficient (D) in the surface region is proportional to the square of the zinc concentration (C), that is D^C2; while there exits the relationship of D∝C in the tail region. The analysis revealed that the formation mechanism of the box profiles is the same as that of the tail region of the kink-and-tail profiles, the same PL signals related to the Ga excess were found in the above two regions, which demontrated that zinc atoms diffused through the kick-out mechanism.Our investigation found that the diffusion mechanism of zinc in GaAs is similar to that in GaSb, while it is different from that in InAs. Zinc diffusion profiles in InAs will show box shapes whether the pure zinc or Zn-In alloy were used as the diffusion sources. For the box profiles obtained under Zn-In sources, there exists the relations of D∝C in the whole region and will not appear the relation of D∝C-2in the shallow region.Sincethe formation of high-concentration surface diffusion regions can be suppresed by Ga atoms in diffuison sources, we proposed a sealed diffusion method using the Zn-Ga alloy sources to fabricate GaSb infrared cells. In the traditional fabrication process for GaSb cells, the pseudo-closed diffuison method using Zn-Sb alloy sources were used to prepare the PN junction. The zinc diffuison profiles will show kink-and-tail shapes with a surface high-concentration diffusion region before the kink point, the precise etching process were needed for etching the surface region to the kink point in order to improve the quantum efficiency of GaSb cells. However, it is difficult to realize pricise etching for the several hunred nanometers region. We used the sealed-quartz-tube diffuison method with Zn-Ga alloy sources to fabricate the PN junction of GaSb cells, which simplified the fabrication processes. The GaSb cells fabricated can maintain a stable electrical output performance, which is useful for volume production. The bandgap of InAs is lower than that of GaSb, thus the infrared cells manufactured using the InAs substrates can be used in a low-temperature thermophotovoltaic system.更多还原