Superior device characteristics have been demonstrated with a novel Al(In)N/GaN-based steep fin-type high electron mobility transistor (HEMT) with a fin width (W _fin ) of 120 nm, a fin height (H _fin ) of 250 nm, and a gate length (L _G ) of 200 nm. The proposed device achieved very low drain leakage(I _off ) <; 8×10 ^-8 A/mm at 7 V and <;1×10 ^-6 A/mm at 100 V, which is four orders of improvement over I _OFF of conventional Al(In)N/GaN HEMTs. In addition, the device exhibits a high ON-state current (I _ON ) of 1.12 A/mm, a steep sub-threshold swing (S) of 63 mV/decade, a low drain-induced barrier lowering of 18.5 mV/V, and a high power-gain cutoff frequency (f _T ) of 21 GHz.

Y-doped SnO₂ thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO₂ films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO₂ semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO₂ thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive V_th shift.

A polycrystalline silicon (poly-Si) capacitorless one-transistor dynamic random-access memory (1T DRAM) has been successfully fabricated and characterized. The proposed 1T DRAM is based on the metal-oxide-semiconductor field-effect transistor (MOSFET) with heavily-doped n+ source and drain junctions, nearly intrinsic n- channel, 500-nm gate length (LG), and 50-nm poly-Si body thickness (Tbody). The floating-body for storing charges was schemed in the silicon-on-insulator (SOI)-like environment which was simply realized by deposited buried oxide and poly-Si layers for the high cost-effectiveness. The program and erase operations are performed by band-to-band tunneling and drift-diffusion mechanisms, respectively, and the retention is assisted by grain boundaries (GBs) capable of charge trapping not solely depending on recombination in Si. The proposed cell achieved an initial sensing margin of 3.2 μA/μm and a long retention time of 1.2 s. The thin-body poly-Si 1T DRAM with full Si processing compatibility has the strong candidacy for the embedded DRAM in the advanced integrated systems.

Sol-gel-processed Mg-doped SnO₂ thin-film transistors (TFTs) were successfully fabricated. The effect of Mg concentration on the structural, chemical, and optical properties of thin films and the corresponding TFT devices was investigated. The results indicated that an optimal Mg concentration yielded an improved negative bias stability and increased optical band gap, resulting in transparent devices. Furthermore, the optimal device performance was obtained with 0.5 wt% Mg. The fabricated 0.5 wt% Mg-doped SnO₂ TFT was characterized by a field effect mobility, a subthreshold swing, and I_on/I_off ratio of 4.23 cm²/Vs, 1.37 V/decade, and ~1 × 10⁷, respectively. The added Mg suppressed oxygen-vacancy formation, thereby improving the bias stability. This work may pave the way for the development of alkaline-earth-metal-doped SnO₂-based thin-film devices.

To increase the radio-frequency (RF) performance of AlGaN/GaN-based fin-type high electron mobility transistors (HEMTs), a novel T-gate process was developed and applied to fabricate a device with high RF performance. In a single lithography process, the applied T-gate process shows a technique for forming a T-gate using the reactivity difference of several photoresists. The fabricated device has a steep fin width (Wfin) of 130 nm, a fin height (Hfin) of 250 nm, and a gate length (LG) of 190 nm. The device exhibits a low leakage current (Ioff) of 6.6 × 10−10 A/mm and a high Ion/Ioff current ratio of 4.7 × 108. Moreover, the fabricated device achieved a high cut-off frequency (fT) of 9.7 GHz and a very high maximum oscillation frequency (fmax) of 27.8 GHz. The fmax value of the proposed device is 138% higher than that of GaN-based fin-type HEMTs without T-gate.