Potassium acceptor doping of ZnO crystals

Abstract

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 1016 cm−3. IR measurements show a local vibrational mode (LVM) at 3226 cm−1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm−1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Green photoluminescence in ZnO crystals: a combined study using positron annihilation, photoluminescence, and hall measurements

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Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

“…Hall measurement was not possible due to the high resistivity and low Hall voltage on these ZnO crystals. Few other groups have reported their experimental work and first-principles calculations for alkali metals doping (Li, Na, and K) in ZnO41424344. Park et al 45.…”

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“…Many researcher have focused on the preparation of p-type ZnO by doping ZnO with various element (such as: N, P, As, Sb, Li, Na, and K). [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] However, the drawback in ZnO is the presence of zinc interstitial (Zn i ) defect and oxygen vacancy defect (V o ) which makes it difficult to prepare p-type ZnO film. Among the various dopants for p-type ZnO films, N is the most potential since the ionic radii is close to the ionic radii of oxygen.…”