Preparation Of P-type Transparent Conducting SnO₂ Thin Films By Spray-pyrolysis

With the development of semiconductor technology, wide band-gap semiconductor materials have been a researched hotspot, attracting many researchers' interest. Tin oxide, as a wide band-gap material, has been widely used in many fields, such as opto-electric devices, high temperature devices, LCD, solar cell, and window coating and so on, for its good properties. Up to now, most researches and applications are based on its n type conducting character, and its low resistance properties. According to our knowledge, few papers and application have been published about SnO₂ based on its p type conducting character. Our group once reported p-type SnO₂ thin films deposited by sol-gel method. It has low mobility, low conducting and films easily to be cracked. To improve these shortcomings, in this paper, spraying pyrolysis has been used to prepare p-type SnO₂ films.In detail, Indium doped SnO₂ films and Indium and Gallium co-doped SnO₂ films were prepared and characterized. Results show that: 1) p-type SnO₂ can be available when the In/Sn ratio is appropriate annealed above 550℃. In this paper, the optimized In/Sn ratio is in the range of 0.06-0.2. The carrier concentration can be up to4×10¹⁸cm^-3 with mobility 0.00732 cm²V^-1s^-1, for In_0.2SnO_x films annealed at 700℃. The mobility is too low because of crystal lattice distortion caused by dopants. The conductance is about 1.49q×10¹⁶Ω^-1cm^-1. 2) Indium and Gallium co-doped SnO₂ films can improve carrier mobility with a little effect on carrier concentration. For In_0.1Sn_0.1O_y films, its carrier concentration is up to +9.5×10¹⁷ cm^-3, with carrier mobility up to 39.2 cm²V^-1s^-1 annealed at 500℃ Compared to the In_0.2SnO_x, the conductance of In_0.1Sn_0.1O_y is up to 3.72q×10¹⁹Ω^-1cm^-1.