[18p-Z09-1~14] 3.9 Terahertz technologies

▲ [18p-Z09-8] Terahertz emission from GaInN/GaN multiple quantum wells studied by wavelength-tunable terahertz emission spectroscopy

〇(D)Abdul Mannan¹, Filchito Renee G. Bagsican¹, Kota Yamahara¹, Iwao Kawayama¹, Hironaru Murakami¹, Heiko Bremers², Uwe Rossow², Andreas Hangleiter², Dmitry Turchinovich³, Masayoshi Tonouchi¹ (1.ILE, Osaka Univ. Japan, 2.TU Braunschweig, Germany, 3.Bielefeld Univ. Germany)

Keywords:GaxIn1-xN/GaN MQW, 1h-1e, 1h-2e optical exciation, terahertz emission

Ga_xIn_1-xN/GaN multiple quantum wells (MQW) are an active ingredient for enhancing the efficiency of optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes (LDs) [1]. However, the lattice mismatch and piezoelectric nature of GaxIn1-xN and GaN cause a strong built-in piezoelectric-field inside MQWs and a quantum-confined stark effect (QCSE) [2]. Both QCSE and built-in piezoelectric-field simultaneously reduce the overall overlap of 1h-1e electron and hole wave functions, so the 1h-2e optical transitions during optical excitation happen, which in reality are parity–forbidden transitions [3]. Dynamical screening of the built-in piezoelectric field by 1h-1e and 1h-2e transition, using ultrafast optical excitation leads to terahertz radiation [4]. In this work, we used laser wavelength-tunable terahertz emission spectroscopy to study photon energy dependence, terahertz emission at various quantum well widths (Lz) assisted by 1h-1e, and 1h-2e transitions. The detailed experimental setup is explained elsewhere [5]. Figure 1(a) shows the sample structure used in this experiment. We used three samples with a variation of only L_z (L_z = 1.5nm, 2.4nm, and 3.0nm). We observed strong terahertz emission dependence of L_z with 1h-2e optical transitions at various photon energy.
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[3] G. Weng, et al., Opt. Express, vol. 25, no. 20, 2017.
[4] D. Turchinovich et al., Phys. Rev. B - Condens. Matter Mater. Phys., vol. 68, no. 24, pp. 1–4, 2003.
[5] H. Murakami et al., ,” J. Phys. D. Appl. Phys., vol. 47, no. 37, p. 374007, Sep. 2014.