Roshko Alexana, Brubaker Matt D, Blanchard Paul T, Harvey Todd E, Bertness Kris A
Physical Measurement Laboratory, National Institute of Standards and Technology 325 Broadway, Boulder, CO, 80305, USA.
Phys Status Solidi B Basic Solid State Phys. 2019;257. doi: 10.1002/pssb.201900611.
The crystallographic polarity of AlN grown on Si(111) by plasma assisted molecular beam epitaxy is intentionally inverted from N-polar to Al-polar at a planar boundary. The position of the inversion boundary is controlled by a two-step growth process that abruptly changes from Al-rich to N-rich growth conditions. The polarity inversion is induced by the presence of Si, which is incorporated from an Al-Si eutectic layer that forms during the initial stages of AlN growth and floats on the AlN surface under Al-rich growth conditions. When the growth conditions change to N-rich the Al and Si in the eutectic react with the additional N-flux and are incorporated into the solid AlN film. Relatively low levels of Al-Si eutectic formation combined with lateral variations in the Si incorporation lead to nonuniformity in the polarity inversion and formation of surprisingly narrow, vertical inversion domains. The results suggest that intentional incorporation of uniform layers of Si may provide a method for producing polarity engineered nitride structures.
通过等离子体辅助分子束外延在Si(111)上生长的AlN的晶体极性在平面边界处有意地从N极性反转到Al极性。反转边界的位置由两步生长过程控制，该过程从富Al生长条件突然转变为富N生长条件。极性反转是由Si的存在引起的，Si来自在AlN生长初始阶段形成并在富Al生长条件下漂浮在AlN表面的Al-Si共晶层。当生长条件变为富N时，共晶中的Al和Si与额外的N通量反应并并入固态AlN膜中。相对较低水平的Al-Si共晶形成与Si掺入的横向变化导致极性反转不均匀，并形成令人惊讶的狭窄垂直反转畴。结果表明，有意掺入均匀的Si层可能提供一种制造极性工程化氮化物结构的方法。
