Thermal Atomic Layer Deposition of Gallium Nitride Films Using Tris(dimethylamido)Gallium and Ammonia

Abstract

Gallium nitride (GaN) is a III-V semiconductor material with a wide and direct bandgap, relatively high carrier mobility, and high breakdown voltage. GaN is suitable for applications in optoelectronic devices and power devices, including light-emitting diodes (LEDs) and high electron mobility transistors (HEMTs). Typically, epitaxial GaN layers are grown by metal-organic chemical vapor deposition (MOCVD) at high deposition temperatures. However, low-temperature growth of GaN is necessary for temperature-sensitive devices and substrates. Atomic layer deposition (ALD) is a technique that offers unique advantages, such as low process temperature, excellent conformality, and atomic-level thickness control.In this study, we investigated the thermal ALD process of GaN at a low temperature of 200°C. Tris(dimethylamido)gallium (TDMAGa) was selected as the Ga precursor because tris(dimethylamido)titanium and tris(dimethylamido)aluminum were successfully adopted in the low-temperature ALD process of TiN and AlN thin films [1]. The growth and properties of ALD GaN films were investigated. ALD GaN films exhibited a self-limiting reaction with a deposition rate of 1.34 Å/cycle at 200°C, with a refractive index of 2.07. The saturation times for TDMAGa and NH3 pulses were 5 s and 30 s, respectively. Deposition at 250°C showed a deposition rate higher than 3 Å/cycle due to the thermal decomposition of TDMAGa. The ALD GaN film deposited at 200°C was amorphous and nitrogen deficient. To improve the crystallinity and composition, the as-deposited GaN films were annealed in an NH3 atmosphere in the deposition chamber without air exposure. The effects of annealing on the crystallinity and composition of the films were investigated. Acknowledgments This work was supported by Samsung Display Co., Ltd.