Transmorphic epitaxial growth of AlN nucleation layers on SiC substrates for high-breakdown thin GaN transistors

Abstract

Interfaces containing misfit dislocations deteriorate electronic properties of heteroepitaxial wide bandgap III-nitride semiconductors grown on foreign substrates, as a result of lattice and thermal expansion mismatches and incompatible chemical bonding. We report grain-boundary-free AlN nucleation layers (NLs) grown by metalorganic chemical vapor deposition on SiC (0001) substrates mediated by an interface extending over two atomic layers L1 and L2 with composition (Al 1/3 Si 2/3 ) 2/3 N and (Al 2/3 Si 1/3 )N, respectively. It is remarkable that the interfaces have ordered vacancies on one-third of the Al/Si position in L1, as shown here by analytical scanning transmission electron microscopy and ab initio calculations. This unique interface is coined the out-of-plane compositional-gradient with in-plane vacancy-ordering and can perfectly transform the in-plane lattice atomic configuration from the SiC substrate to the AlN NL within 1 nm thick transition. This transmorphic epitaxial scheme enables a critical breakdown field of $2 MV/cm achieved in thin GaN-based transistor heterostructures grown on top. Lateral breakdown voltages of 900 V and 1800 V are demonstrated at contact distances of 5 and 20 lm, respectively, and the vertical breakdown voltage is !3 kV. These results suggest that the transmorphic epitaxially grown AlN layer on SiC may become the next paradigm for GaN power electronics.

Epitaxial GaN using Ga(NMe2)3 and NH3 plasma by atomic layer deposition

“…This is on par with previous high temperature CVD study of GaN films were an AlN seed layer was deposited on the SiC substrate. 8 These findings could revolutionize the transistor industry, especially for the production of high electron mobility transistors (HEMTs). Being able to deposit very thin GaN directly on SiC without the need for an AlN seed layer allows for increased design freedom when producing HEMTs, which could in turn improve their performance.…”

“…6 Therefore, an AlN buffer layer is used to facilitate GaN growth. [7][8][9] Currently, thin films of electronic grade epitaxial GaN are deposited by chemical vapor deposition (CVD) processes using trimethylgallium (TMG) and ammonia (NH 3 ) at temperatures between 800-1000 1C. 10 The high deposition temperatures are required to obtain highly crystalline films but also to overcome the poorly suited precursor combination of TMG and NH 3 , which leads to high N/Ga precursor ratios of 10 3 .…”

Epitaxial GaN using Ga(NMe2)3 and NH3 Plasma by Atomic Layer Deposition

“…This is on par with previous high temperature CVD study of GaN films were an AlN seed layer was deposited on the SiC substrate. 8 . These findings could revolutionize the transistor industry, especially for the production of high electron mobility transistors (HEMTs).…”

“…6 Therefore, an AlN buffer layer is used to facilitate GaN growth. 7,8,9 Currently, thin films of electronic grade epitaxial GaN are deposited by chemical vapor deposition (CVD) processes using trimethylgallium (TMG) and ammonia (NH3) at temperatures between 800-1000 C. 10 The high deposition temperatures are required to obtain highly crystalline films but also to overcome the poorly suited precursor combination of TMG and NH3, which leads to high N/Ga precursor ratios of 10 3 .…”

Epitaxial GaN using Ga(NMe2)3 and NH3 Plasma by Atomic Layer Deposition

“…6 Therefore, an AlN buffer layer is used to facilitate GaN growth. 7,8,9 Currently, thin films of electronic grade epitaxial GaN are deposited by chemical vapor deposition (CVD) processes using trimethylgallium (TMG) and ammonia (NH3) at temperatures between 800-1000 C. 10 The high deposition temperatures are required to obtain highly crystalline films but also to overcome the poorly suited precursor combination of TMG and NH3, which leads to high N/Ga precursor ratios of 10 3 .…”