Browsing by Subject "Field-effect transistors"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Open Access Ligand exchange and impurity doping in 2d cdse nanoplatelet thin films and their applications(Wiley-VCH Verlag GmbH & Co. KGaA, 2021-09-23) Lee, W, S.; Kang, Y-G.; Lee, Y. M.; Jean, S.; Sharma, A.; Demir, Hilmi Volkan; Han, M. J.; Koh, W-K.; Oh, S. J.The effects of halide-ligand exchange and Cu and Ag doping are studied on structural, optical, and electrical properties of four monolayer CdSe nanoplatelet (NPL) and NPL thin films. Combinational study shows that NH4Cl-treatment on CdSe NPL and NPL thin films show tetragonal lattice distortion of NPL, side-to-side attachment between NPLs, bathochromic shift in absorption spectra, and complete quenching of band-edge and dopant-induced emissions. First-principle calculations reveal that Cl creates states below valence band maximum while Ag and Cu dopants create acceptor-like states, explaining the change of their optical property. Field-effect transistors are fabricated to investigate the effect of doping and reduced interplatelet distance on electrical properties of CdSe NPL thin films, demonstrating Cu and Ag dopants mitigate n-type character of CdSe NPL thin films. Temperature-dependent electrical characterization is conducted to further understand charge transport behavior depending on the existence of dopants. This work provides scientific information on the influence of surface chemistry and impurity doping on quantum confined semiconductors and new directions for the design of high-performance nanomaterial-based electronic and optoelectronic devices.Item Open Access Nanometer-thick ınsertion layer for the effective passivation of surface traps and ımproved edge acuity for AlGaN/GaN HEMTs(Institute of Electrical and Electronics Engineers, 2023-09-30) Odabaşı, Oğuz; Ghobadi, Amir; Ghobadi, Türkan Gamze Ulusoy; Güneysu, Efkan; Urfalı, Emirhan; Yağlıoğlu, Gül; Bütün, Bayram; Özbay, EkmelIn AlGaN/GaN high electron mobility transistors (HEMTs), the existence of long lifetime surface traps can cause several adverse effects, including threshold voltage ( Vth ) instability and current collapse. Therefore, understanding the nature and lifetime of these traps is crucial to provide effective passivation. In this work, the nature of these traps is scrutinized by combining femtosecond transient optical and multiple structural analyses. Later, using a nanometer-thick Al2O3 insertion layer, these traps are effectively passivated. In order to observe the effect of the proposed passivation on device performance, HEMT devices were fabricated. As a result of this passivation, better edge acuity in ohmic contacts and protection of the surface of the epitaxy were achieved. The lag performance of the HEMT devices was significantly improved. It was found that the drain lag was reduced from 37.1% (for the standard SiNx passivated design) to 10.4% for the modified HEMT design. In operating this transistor as a power amplifier, nearly no change in the quiescent bias point was observed after consecutive load–pull measurements, which shows the stability of the fabricated device.