# Metal-Insulator Transition in Ga doped ZnO via Controlled Thickness

## TL;DR

This study investigates the thickness-dependent metal-insulator transition in Ga-doped ZnO thin films, revealing different conduction mechanisms and localization phenomena as the film thickness varies, supported by experimental and computational analysis.

## Contribution

It demonstrates how film thickness influences conduction mechanisms and localization effects in Ga:ZnO, combining experimental transport measurements with density functional theory calculations.

## Key findings

- Thinnest films exhibit insulating behavior with VRH conduction.
- Thicker films show metallic conduction with weak localization.
- Surface reconstruction and doping induce disorder affecting electron mobility.

## Abstract

We report thickness dependent metal insulator transition in Ga doped ZnO (Ga:ZnO) thin films grown by pulsed laser deposition technique. From the electrical transport measurements, we find that while the thinnest film exhibits a resistivity of 0.05 $\Omega$-cm, lying in the insulating regime, the thickest has resistivity of $6.6\times10^{-4}\Omega$-cm which shows metallic type of conduction. Our analysis reveals that the Mott's variable range hopping (VRH) model governs the insulating behavior in the thinner Ga:ZnO whereas the 2D weak localization phenomena is appropriate to explain the electron transport in the thicker Ga:ZnO. Magnetoresistance study further confirms the presence of strong localization in 6 nm film while weak localization is observed in 20 nm and above thicker films. From the density functional calculations, it is found that due to surface reconstruction and Ga doping, strong crystalline disorder sets in very thin films to introduce localized states and thereby, restricts the donor electron mobility.