Abstract
Epitaxial nanometer-thin indium nitride (InN) films are considered promising active layers in various device applications but remain challenging to deposit. We compare the morphological evolution and characterizations of InN films with various growth conditions in chemical vapor deposition (CVD) by both a plasma atomic layer deposition (ALD) approach and a conventional metalorganic CVD approach. Our results show that a time-resolved precursor supply is highly beneficial for deposition of smooth and continuous InN nanometer-thin films. The time for purging the reactor between the precursor pulses and low deposition temperature are key factors to achieve homogeneous InN. The gas exchange dynamics of the reactor is further studied using computational fluid dynamics. According to our study, 320 °C is found to be the upper temperature where the dynamics of the deposition chemistry can be controlled to involve only surface reactions with surface species. The results highlight the promising role of the ALD technique in realizing electronic devices based on nanometer-thin InN layers.
Highlights
III-nitrides (AlN, GaN, and indium nitride (InN)) and their alloys are prominent semiconductor materials
Note that the dimension of the islands deposited by chemical vapor deposition (CVD) at 450 °C is much smaller than the droplets (1−2 μm) found on the sample deposited by atomic layer deposition (ALD) at 450 °C
We show that a time-resolved CVD approach by plasma ALD affords InN films with superior morphology and crystalline quality compared to a conventional, continuous CVD approach by standard thermal metalorganic CVD
Summary
III-nitrides (AlN, GaN, and InN) and their alloys are prominent semiconductor materials. The revised bandgap of InN to 0.7 eV1 and its high-electron mobility open up new opportunities, such as IR emitters, sensors, solar cells, thin-film transistors, and high-electron mobility transistors.. The revised bandgap of InN to 0.7 eV1 and its high-electron mobility open up new opportunities, such as IR emitters, sensors, solar cells, thin-film transistors, and high-electron mobility transistors.7 As all such applications are based on heterostructures with homogeneous coverage of nanoscale active layers, highly controlled InN epitaxy is paramount to realize any application. The growth of InN is problematic due to its low thermal stability; InN decomposes to In metal and nitrogen gas at about 550 °C.8. This has been manifested by its high equilibrium pressure with nitrogen which has led to attempts at depositing InN at very high nitrogen pressures.. The growth of InN is problematic due to its low thermal stability; InN decomposes to In metal and nitrogen gas at about 550 °C.8 This has been manifested by its high equilibrium pressure with nitrogen which has led to attempts at depositing InN at very high nitrogen pressures. Due to slow decomposition kinetics of ammonia (NH3), the most common nitrogen precursor in chemical vapor deposition (CVD), N/In ratios in the order of >104 have often been used in CVD of InN. Alternative N-precursors, such as dimethylhydrazine and tertiarybuthylhydrazine, have been shown ineffective for the growth of InN. To allow more reactive
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