Nondegenerate Polycrystalline Hydrogen-Doped Indium Oxide (InOx:H) Thin Films Formed by Low-Temperature Solid-Phase Crystallization for Thin Film Transistors

We successfully demonstrated a transition from a metallic InOx film into a nondegenerate semiconductor InOx:H film. A hydrogen-doped amorphous InOx:H (a-InOx:H) film, which was deposited by sputtering in Ar, O-2, and H-2 gases, could be converted into a polycrystalline InOx:H (poly-InOx:H) film by low-temperature (250 degrees C) solid-phase crystallization (SPC). Hall mobility increased from 49.9 cm(2)V(-1)s(-1) for an a-InOx:H film to 77.2 cm(2)V(-1)s(-1) for a poly-InOx:H film. Furthermore, the carrier density of a poly-InOx:H film could be reduced by SPC in air to as low as 2.4 x 10(17) cm(-3), which was below the metal-insulator transition (MIT) threshold. The thin film transistor (TFT) with a metallic poly-InOx channel did not show any switching properties. In contrast, that with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. For the InOx:H TFTs with a channel carrier density close to the MIT point, maximum and average field effect mobility (mu(FE)) values of 125.7 and 84.7 cm(2)V(-1)s(-1) were obtained, respectively. We believe that a nondegenerate poly-InOx:H film has great potential for boosting the mu(FE) of oxide TFTs.

Automated summary

The study demonstrated the conversion of a metallic indium oxide film into a nondegenerate semiconductor indium oxynitride film. By solid-phase crystallization, the Hall mobility was increased and carrier density was reduced, leading to improved field effect mobility in oxide thin film transistors.