Realizing n-type gete through suppressing the formation of cation vacancies and bi-doping*

It is known that p-type GeTe-based materials show excellent thermoelectric performance due to the favorable electronic band structure. However, n-type doping in GeTe is of challenge owing to the native Ge vacancies and high hole concentration of about 1021 cm−3. In the present work, the formation energy of cation vacancies of GeTe is increased through alloying PbSe, and further Bi-doping enables the change of carrier conduction from p-type to n-type. As a result, the n-type thermoelectric performance is obtained in GeTe-based materials. A peak zT of 0.34 at 525 K is obtained for (Ge0.6Pb0.4)0.88Bi0.12Te0.6Se0.4. These results highlight the realization of n-type doping in GeTe and pave the way for further optimization of the thermoelectric performance of n-type GeTe.

A Comprehensive Density-of-States Model for Oxide Semiconductor Thin Film Transistors

In this paper, a comprehensive Density of States model was proposed to understand the origin of conductivity and the performance of p-type and n-type oxide semiconductor thin film transistors (TFTs). To validate the model, the simulated I-V characteristics are compared with measured results of p-type Cu2O & SnO and n-type SnO2 TFTs. It was found that cation vacancies were responsible for hole conduction in p-type TFTs, while anion vacancies and/or metal interstitial were responsible for electron conduction in n-type TFTs. This was observed by assigning the cation vacancies to acceptor-like Gaussian states and anion vacancies and/or metal interstitial to Donor-like Gaussian states respectively. The characteristic slopes in conduction/valence band-tail states are due to disorders present in the oxide semiconductors. The model is successfully delivering the physical insight and path way to circuit simulation of large scale integration of pixel circuits AMLCD/AMOLED displays.

Iron cation vacancies in Pt(iv)-doped hematite

Platinum-doping of hematite (α-Fe2O3) is a popular method to increase the performance of hematite in photoelectrochemical applications. Here we show that the additional charge caused by Pt4+ is balanced by an Fe3+ vacancy.