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Temperature dependence of stacking faults in catalyst-free GaAs nanopillars

机译：无催化剂GaAs纳米柱中的堆垛层错的温度依赖性

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摘要

Impressive opto-electronic devices and transistors have recently been fabricated from GaAs nanopillars grown by catalyst-free selective-area epitaxy, but this growth technique has always resulted in high densities of stacking faults. A stacking fault occurs when atoms on the growing (111) surface occupy the sites of a hexagonal-close-pack (hcp) lattice instead of the normal face-centered-cubic (fcc) lattice sites. When stacking faults occur consecutively, the crystal structure is locally wurtzite instead of zinc-blende, and the resulting band offsets are known to negatively impact device performance. Here we present experimental and theoretical evidence that indicate stacking fault formation is related to the size of the critical nucleus, which is temperature dependent. The difference in energy between the hcp and fcc orientation of small nuclei is computed using density-function theory. The minimum energy difference of 0.22 eV is calculated for a nucleus with 21 atoms, so the population of nuclei in the hcp orientation is expected to decrease as the nucleus grows larger. The experiment shows that stacking fault occurrence is dramatically reduced from 22% to 3% by raising the growth temperature from 730 to 790 ° C. These data are interpreted using classical nucleation theory which dictates a larger critical nucleus at higher growth temperature.
机译：令人印象深刻的光电器件和晶体管最近是由通过无催化剂的选择性区域外延生长的GaAs纳米柱制成的，但是这种生长技术始终导致高密度的堆垛层错。当增长的（111）表面上的原子占据六方密堆积（hcp）晶格的位置而不是正常的面心立方（fcc）晶格位置时，就会发生堆叠错误。当连续发生堆垛层错时，晶体结构是局部纤锌矿而不是闪锌矿，并且已知带隙偏移会对器件性能产生负面影响。在这里，我们提供实验和理论证据，表明堆垛层错的形成与临界核的大小有关，而临界核的大小与温度有关。小核的hcp和fcc取向之间的能量差是使用密度函数理论计算的。对于具有21个原子的原子核，计算出的最小能量差为0.22 eV，因此在hcp方向上的原子核总数预计会随着原子核的增大而减少。实验表明，通过将生长温度从730°C升高到790°C，堆垛层错的发生率从22％显着降低到3％。这些数据使用经典的成核理论解释，该理论要求在更高的生长温度下具有更大的临界核。

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