Tin Monoxide Thin-film Transistors Research Articles

High mobility p-channel tin monoxide thin-film transistors with hysteresis-free like behavior

In this Letter, we report a demonstration of p-channel tin monoxide (SnO) thin-film transistors (TFTs) with high field-effect mobility (μFE) exceeding 10 cm2/Vs and hysteresis-free like behavior. We demonstrate that maintaining metallic states before encapsulation is a key process to enhance μFE in p-type SnO thin-films. Sustaining this meta-stability involves the following two processes during fabrication: (1) postdeposition annealing (PDA) in two steps and (2) encapsulation in the middle of each PDA. This simple process not only suppresses creation of oxidized states such as adverse Sn4+ but also facilitates the lateral growth of crystals with improved crystallinity by interfacial energy stabilization. The resultant SnO TFT reveals a record-high μFE up to 15.8 cm2/Vs with a negligible hysteresis of 0.1 V. This study suggests a practical route to grant high μFE to p-channel SnO TFTs without any dopant or complex postdeposition treatment.

Highly Optimized Complementary Inverters Based on p-SnO and n-InGaZnO With High Uniformity

Oxide semiconductors are desirable for large-area and/or flexible electronics. Here, we report highly optimized complementary inverters based on n-type indium–gallium–zinc oxide and p-type tin monoxide thin-film transistors. Oxide-based inverters with a record voltage gain of 142 have been achieved. The switching point voltage has also been tuned to reach the ideal value, namely half value of the supply voltage. A narrow transition width of 1.04 V (13% of the supply voltage) is achieved which offers a strong anti-jamming ability to avoid logic errors. Rail-to-rail output voltage swing has been achieved. The inverters still maintain high performance at a low supply voltage of 6 V. A very large number of inverters have been fabricated and showed excellent uniformity in a working area of 1 cm $\times $ 1 cm. The switching point voltage and transition width show very small standard deviations of only 0.55% (0.022 V) and 2.3% (0.024 V), respectively, demonstrating promises for large-scale circuit integration.

Analysis of Carrier Transport Mechanism for p-Type SnO Thin-Film Transistor

Temperature effect on the I-V characteristics of tin monoxide thin film transistors (SnO TFTs) has been analyzed. The result shows that the drain current of the SnO TFT obeys the Meyer-Neldel rule under low temperature, where current conduction is a thermally activated process. The carrier transport would be dominated by multiple trapping conduction, while, percolation conduction mechanism holds as the temperature increase.

Charge Transport Mechanism in p-Channel Tin Monoxide Thin-Film Transistors

In this letter, we report on the charge transport mechanism in the p-type tin monoxide (SnO) thin-film transistors (TFTs) over a wide range of operation regimes and temperatures. From the temperature-dependent field-effect conductance measurements, the variable range hopping and the trap-limited band transport are considered as dominant charge transport mechanisms in the SnO TFT at temperatures below ~ 200 K (−73 °C) and above ~273 K (0 °C), respectively, in the subthreshold and transition regions. In the above-threshold region, the intrinsic field-effect mobility ( $\mu _{\mathsf {FEi}})$ decreases with an increase in temperature with a prefactor $\gamma \sim $ -0.36 in the $\mu _{\mathsf {FEi}}\sim {T}^{\gamma }$ law at temperatures ( ${T}\text{s}$ ) between RT and 353 K (80 °C). The observed temperature and gate overdrive voltage dependence of $\mu _{\mathsf {FEi}}$ suggests that the acoustic phonon scattering is the dominant physical mechanism limiting $\mu _{\mathsf {FEi}}$ in the p-type SnO TFT at realistic operating conditions [in the above-threshold region and at temperatures ranging from RT to 353 K (80 °C)].

Analysis of carrier transport and band tail states in p-type tin monoxide thin-film transistors by temperature dependent characteristics

Tin monoxide (SnO) has drawn much attention in recent years due to its high hole mobility, transparency, and potential for mass production. However, due to its metastable nature, the deposited film often contains multi-phases such as metallic tin and tin dioxide, which may degrade its electrical properties. Here, we presented the temperature dependent characteristics of p-type SnO thin-film transistors. The hole transport mechanism is dominated by band conduction at high temperatures and variable-range hopping at low temperatures. The maximum activation energy was found to be 308 meV, which denotes a bandgap of around 0.6 eV. The density of states was found to be 1.12 × 1021 cm−3 eV−1 at VG = −80 V, and 6.75 × 1020 cm−3 eV−1 at VG = 0 V, respectively.

Subgap states in p-channel tin monoxide thin-film transistors from temperature-dependent field-effect characteristics

This paper experimentally investigates the subgap density of states (DOS) in p-type tin monoxide (SnO) thin-film transistors (TFTs) for the first time by using temperature-dependent field-effect measurements. As the temperature increases, the turn-on voltage moves in the positive direction, and the off-current and subthreshold slope continuously increase. We found that the conductivity of the SnO TFT obeys the Meyer–Neldel (MN) rule with a characteristic MN parameter of 28.6 eV−1 in the subthreshold region, from which we successfully extracted the subgap DOS by combing the field-effect method and the MN relation. The extracted subgap DOS from fabricated p-type SnO TFTs are exponentially distributed in energy, and exhibit around two orders of magnitude higher values compared to those of the n-type amorphous indium–gallium–zinc oxide TFTs.