Investigation of defects in In–Ga–Zn oxide thin film using electron spin resonance signals

Abstract

In–Ga–Zn oxide (IGZO) is a next-generation semiconductor material seen as an alternative to silicon. Despite the importance of the controllability of characteristics and the reliability of devices, defects in IGZO have not been fully understood. We investigated defects in IGZO thin films using electron spin resonance (ESR) spectroscopy. In as-sputtered IGZO thin films, we observed an ESR signal which had a g-value of g = 2.010, and the signal was found to disappear under thermal treatment. Annealing in a reductive atmosphere, such as N2 atmosphere, generated an ESR signal with g = 1.932 in IGZO thin films. The temperature dependence of the latter signal suggests that the signal is induced by delocalized unpaired electrons (i.e., conduction electrons). In fact, a comparison between the conductivity and ESR signal intensity revealed that the signal's intensity is related to the number of conduction electrons in the IGZO thin film. The signal's intensity did not increase with oxygen vacancy alone but also with increases in both oxygen vacancy and hydrogen concentration. In addition, first-principle calculation suggests that the conduction electrons in IGZO may be generated by defects that occur when hydrogen atoms are inserted into oxygen vacancies.

Origin of major donor states in In–Ga–Zn oxide

“…Through a constant photocurrent method (CPM), the creation of V O was confirmed by estimating absorption coefficient of deep level states derived from oxygen vacancies. 18 The conductivity of the unannealed (as-deposited) sample is below the detection limits (1 Â 10 À2 S/m). The as-deposited film has very low conductivity, in spite of its high H concentration (7 Â 10 19 atoms/cm 3 ).…”

50‐3: Formation of Source and Drain Regions in Top‐Gate Self‐Aligned Oxide Semiconductor Field‐Effect Transistor

“…Figure 2 shows the estimated spin densities. During the ESR analysis, a signal was observed at g  1.93 in the SiN/OS film, indicating the presence of conduction electrons owing to the hydrogen trapped in oxygen vacancies (Vo) (hereinafter such hydrogen is referred to as VoH) that is a donor in the OS film [16,17]. The ESR signal was not observed in the SiON/OS film.…”

Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices

“…The majority carriers in ZnO:Al are known to originate from the extrinsic substitution of Al on the Zn site 40 41 . In contrast, the donor defect in a-IGZO is widely considered to be strongly tied to intrinsic oxygen vacancy defects, resulting in the carrier concentration being oxygen sensitive 39 42 43 44 . As a result, while both materials are sensitive to oxygen within their structure, due to oxygen interstitials acting as electron pinning defects, it is expected that the a-IGZO would show a significantly higher sensitivity.…”