Epitaxial lateral mask overgrowth which occurs during GaN selective epitaxy has been studied using linear mask features. The lateral growth varies between its maximum and minimum over a 30° angular span and exhibits hexagonal symmetry. Vertical growth follows an opposite trend, with lateral growth maxima, and vertical growth minima occurring for lines parallel to the GaN 〈10•0〉. Large variations in the lateral growth are also obtained through variations in the growth temperature and NH3 flow. Under proper growth conditions, lateral to vertical growth rate ratios of up to 4.1 can be achieved, resulting in significant lateral mask overgrowth and coalescence of features without excessive growth times.
A method of lowering the surface barrier for field emission by using the piezoelectric effect is presented. The piezoelectric effect produces a surface dipole that decreases the surface barrier, which in turn decreases the turn-on voltage of the field emitter. Calculations show that significant reduction of the tunneling barrier can be effected with relatively thin layers of strained InGaN on GaN field emitter arrays. Dramatic reduction of the turn-on voltage from 450 V (GaN field emitter array) to 70 V (InGaN/GaN field emitter array) was observed and can be attributed partly to surface barrier lowering.
Articles you may be interested inFabrication and characteristics of lateral type GaN field-emission arrays using metalorganic chemical vapor deposition J.GaN field emission pyramids are grown by self-limiting, selective-area metalorganic chemical vapor deposition. The self-limitation provides the potential of high uniformity of the pyramids and the selective-area growth allows one to define regular arrays of GaN pyramids for field emitter arrays ͑FEAs͒. Fabrication of an integrated anode lowered the operating voltage of the FEAs by narrowing the anode-cathode distance compared to devices with an external anode. A maximum emission current of 0.15 A/tip has been observed for voltages of 570 V with an emitter-anode separation of 2 m.
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