Molecular beam homoepitaxy on bulk AlN enabled by aluminum-assisted surface cleaning

Abstract

We compare the effectiveness of in situ thermal cleaning with that of Al-assisted cleaning of native surface oxides of bulk AlN for homoepitaxial growth by molecular beam epitaxy. Thermal deoxidation performed at 1450 °C in vacuum results in voids in the AlN substrate. On the other hand, Al-assisted deoxidation at ≈900°C results in high-quality AlN homoepitaxy, evidenced by clean and wide atomic terraces on the surface and no extended defects at the growth interface. This study shows that Al-assisted in situ deoxidation is effective in removing native oxides on AlN, providing a clean surface to enable homoepitaxial growth of AlN and its heterostructures; furthermore, it is more attractive over thermal deoxidation, which needs to be conducted at much higher temperatures due to the strong bonding strength of native oxides on AlN.

High conductivity Polarization-induced 2D hole gases in Undoped GaN/AlN Heterojunctions enabled by Impurity Blocking Layers

“…With the rising relevance of AlN as the platform for UV photonics and future RF electronics 8,28 , significant interest exists in using 2DEGs and 2DHGs on AlN to make RF p-channel 7,29 and n-channel transistors 30,31 and enable wide-bandgap RF CMOS type devices. Combining the results of this work with recent advancements in homoepitaxial growths of AlN 32,33 should enable fundamental scientific studies of 2DEGs and 2DHGs in such polar heterostructures and simultaneously enable significant technological advances.…”

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

“…For sample A, no intentional in-situ cleaning was performed, whereas for sample B, Al-assisted surface cleaning was employed before the MBE growth. The Al-assisted surface cleaning consists of multiple cycles of Al adsorption and desorption, similar to earlier reports on Al-polar AlN substrates (19,20). The substrate was first heated up to a thermocouple temperature of 1060 °C without nitrogen gas flow.…”

Very High Density (>1014 cm−2) Polarization‐Induced 2D Hole Gases Observed in Undoped Pseudomorphic InGaN/AlN Heterostructures

“…Although Fischer model can explain the trend in the experimental data in Figure 2b, more experimental points at higher compositions will allow for better comparison to other critical thickness models. [42] The recent advancements [5,18,43] in homoepitaxial growths of AlN provide an ideal platform for such studies in structurally and chemically pure heterostructures.…”