Low Temperature Growth and Conductivity Control of High Quality ZnS Layrs Grown by Using High TemperatureE Molecular Beams

本研究采用分子束外延（MBE）技术在GaAs（001）和错取向GaAs（001）衬底上生长ZnS/GaAs和ZnSe/GaAs外延层，并利用反射高能电子衍射（RHEED）研究了其生长过程，研究了外延层的生长速率和光学性质。本实验使用的分子束是由传统K池出口加装加热器的积液池排出的后加热分子束。Li束作为p型受体掺杂剂，从传统的K电池中使用元素Li注入到生长表面。我们发现弯曲的条纹在MBE生长期间和之后出现在RHEED模式中。弯曲条纹的起源归因于一维li相关晶格，即。， Li原子在表面台阶的b阶边缘被Se原子选择性捕获。此外，如果在GaAs (001) -just表面添加Li原子，层的生长速率会降低，且当Li束流通量超过一定数量时，层的生长不会发生外延生长。这意味着生长具有足够厚度的高掺杂锂层是困难的。生长速率降低的原因是由Li原子终止的b型阻碍了层的生长。然而，我们发现，如果使用错误取向的GaAs衬底（15 off），则不会发生生长速率降低。在掺杂锂的ZnS和ZnSe层中，锂受体结合激子（I_1）的发射、FA和DAP的发射在PL光谱中占主导地位，其他发射非常弱，说明外延层的纯度很高。FA发射的优势意味着供体样杂质如间隙Li的浓度极低。因此，我们可以说，利用后加热分子束生长MBE是一种生长掺杂锂外延层的有效方法。我们还发现在未掺杂znse /GaAs的PL光谱中观察到令人困惑的Iv发射行为，即在PL测量期间发射强度增加。我们得出了Iv发射的发射中心是由Se空位和光激发载流子形成的。少

In this study, , ZnS/GaAs and ZnSe/GaAs epitaxial layrs were grown on GaAs (001) and misoriented GaAs (001) substrates by a molecular beam epitaxy (MBE), and their growth process were studied by means of a reflection high energy electron diffracti on (RHEED) , and the growth rate of epitaxial layr and the optical property were investigated. The molecular beams used in present experiment are post-heated molecular beams exhausted from the effusion cell equipped with extra heater at the outlet of conventional K cell.As P-type acceptor dopant, Li beam is supplied onto the growing surface form conventional K cell using elemental Li. We found that the curved streaks appear in the RHEED pattern during and after MBE growth. The origin of curved streaks are attributed to the one-dimensional Li-related lattice, ie., Li atoms are selectively captured by Se atoms at B-step edge of surface terrace. Furthermore, if Li atoms are suppled on GaAs (001) -just surface, the layr growth rate decreases and … More if Li beam flux exceeds a certain amount, no epitaxial growth takes places. This means that the growth of Li highly doped layr with sufficient thickness is difficult. The reason of growth rate reduction is attributed to the B-type teminated with Li atoms obtacle the layrer growth from these step edges. However, we found that the growth rate reduction does not occur, if the misoriented GaAs substrates (15ﾟoff) are used.In Li-doped ZnS and ZnSe layrs, the emission from Li-acceptor bound exciton (I_1) , FA and DAP emissions dominate the PL sectrum and other emissions are very weak, which denotes the epitaxial layrs are high Purity. The dominace of FA emission means that the concentration of donor-like impurities such as interstitial Li is extremely low. Thus, we can say that the MBE growth using post-heated molecular beams are an effective method to grow Li-doped epitaxial layrs.We also found puzzuling behvior of Iv emiison obserev in the PL spectra of undoped-ZnSe/GaAs, i.e., the emission intensity increases during PL measurement. We concluded that the emission center for Iv emission is formed by Se vacancy and photo-excited carriers. Less