Understanding hydrogen and nitrogen doping on active defects in amorphous In-Ga-Zn-O thin film transistors

Abstract

This work analyses the physics of active trap states impacted by hydrogen (H) and nitrogen (N) dopings in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) and investigates their effects on the device performances under back-gate biasing. Based on numerical simulation and interpretation of the device transfer characteristics, it is concluded that the interface and bulk tail states, as well as the 2þ charge states (i.e., acceptors VO2þ) related to oxygen vacancy (VO),

Defect Self‐Compensation for High‐Mobility Bilayer InGaZnO/In2O3 Thin‐Film Transistor

“…While increasing the sputtering temperature, device performances (e.g., V TH , SS, and threshold voltage difference (Δ V TH ) between the forward and backward curves in hysteresis plots) have been obviously enhanced in the single‐layer IGZO TFT, whereas a large negative shift in the transfer characteristics is observed and high conductivity is induced in the single‐layer In 2 O 3 TFT. Therefore, while increasing the sputtering temperature, the different trends shown in the electrical performances of the two single‐layer TFTs indicate different types of the dominant defects, i.e., the indium‐related defects in In 2 O 3 and the oxygen‐related defects in IGZO . More detailed discussion will be given next.…”

“…In a‐IGZO, one well‐known mechanism is that oxygen vacancies (V O ) dominate in the intrinsic defect framework and dope the material by directly providing electrons to the conduction band, i.e., generating two free electrons and working as the donors . As a result, the added oxygen interstitials (O i ) induced by the V O and the ionized oxygen vacancies (V O + ) act as acceptors and degrade device SS and hysteresis characteristics in the a‐IGZO TFTs, as depicted in Figure a. While increasing the sputtering temperature, these oxygen‐related defect densities can be reduced .…”

15.3: Defect Engineering in n‐Type Oxide Semiconductor TFTs

“…In InGaZnO, zinc vacancy also easily forms as deep acceptor. [3] In ZnO, the dominant native defects are oxygen and zinc vacancies. The zinc vacancy Zn(vac) is deep acceptor and largely degrades the subthreshold slope SS, whereas oxygen vacancies O(vac) behave as deep donors and are mostly neutral and electrically inactive.…”

“…On the contrary, the indium vacancies In(vac) form shallow acceptor levels above the VBM. [1] While implementing the dopants incorporation and the bilayer stack, [3] [4] the defects density inside these n-type oxide semiconductors can be reduced and a barrier height is formed between the hydrogenated and pristine layers, improving the device performances like the current on/off ratio, the field-effect mobility, SS and stability. However, with the continuous H plasma treatment, the H dopants can behave as the positive or negative charge states, leading to various shifting trend in the transfer curves and also device degradation.…”

29.3: Invited Paper: Defect Engineering in n‐Type Oxide Semiconductor TFTs

“…On the contrary, the indium vacancies In(vac) form shallow acceptor levels above the VBM. [1] While implementing the dopants incorporation [3] and the bilayer stack [4] , the defects density inside these n-type oxide semiconductors can be reduced and a barrier height is formed between the hydrogenated and pristine layers, improving the device performances like the current on/off ratio, the fieldeffect mobility, SS and stability. However, with the continuous H plasma treatment, the H dopants can behave as the positive or negative charge states, leading to various shifting trend in the transfer curves and also device degradation.…”