Semiconductors group

Abstract:

Alloying is widely adopted for tuning the properties of emergent semiconductors for optoelectronic and photovoltaic applications. So far, alloying strategies have primarily focused on engineering bandgaps rather than optimizing charge-carrier transport. Here, we demonstrate that alloying may severely limit charge-carrier transport in the presence of localized charge carriers (e.g., small polarons). By combining reflection-transmission and optical pump-terahertz probe spectroscopy with first-principles calculations, we investigate the interplay between alloying and charge-carrier localization in Cs₂AgSb_xBi_1-xBr₆ double perovskite thin films. We show that the charge-carrier transport regime strongly determines the impact of alloying on the transport properties. While initially delocalized charge carriers probe electronic bands formed upon alloying, subsequently self-localized charge carriers probe the energetic landscape more locally, thus turning an alloy's low-energy sites (e.g., Sb sites) into traps, which dramatically deteriorates transport properties. These findings highlight the inherent limitations of alloying strategies and provide design tools for newly emerging and highly efficient semiconductors.

Abstract:

[This corrects the article DOI: 10.1021/acsenergylett.3c01368.].

Abstract:

Optical Pump Terahertz Probe (OPTP) spectroscopy is a well-established measurement technique with which charge-carrier dynamics of semiconductor nanowires (NW) can be extracted in a noncontact manner. Here in this work, we employ OPTP spectroscopy for measuring temperature-dependent photoconductivity spectra of 3D Dirac Cd 3 As 2 semi-metal nanowires, revealing a high Extrinsic carrier concentration of ∼2.0x1017cm−3 and ultrahigh carrier mobility of up to ∼13x103cm2V−1s−1 at a temperature of 5 K.

Abstract:

Topological insulator (TI) materials are emerging as novel materials for spintronic applications. Here, we demonstrate helicity-dependent THz emission from Dirac semi-metal Cd 3 As 2 nanowires and used scattering-type scanning optical microscopy (s-SNOM) to identify potential single nanowire candidates for device applications. The preliminary investigation data of a candidate nanowire shows a homogenous topography and constant dielectric function in the MIR range. Indicating high-quality crystalline growth ideal for topological characterization.