Strikingly Different Behaviors of Photoluminescence Intensity and Terahertz Output Power versus Period of InGaN/GaN Quantum Wells

Factors Affecting Terahertz Emission from InGaN Quantum Wells under Ultrafast Excitation

“…QWs is strongly infuenced by the number of QWs. Te THz emission has been studied for QW samples with up to 16 QW period numbers [31]. It is observed that the increased period number results in an increased piezoelectric feld due to strain accumulation in the respective QWs, leading to higher THz emission.…”

“…Sun et al observed a continuous increase in THz output power with the increase in the QW period number [31]. Tey used a maximum of 16 periods.…”

“…increase Indium content should result in higher THz emission due to increased electron-hole separation leading to higher dipole strength [31]. Norkus et al, on the other hand, found that an increase Indium content can result in the screening of built-in felds due to the high density of electron gas in QWs [41].…”

“…Te THz spectroscopy has applications in environmental monitoring [5], imaging [6], biomedical diagnosis [7], material characterization [8], food inspection [9], medicine inspection [10], communication technologies [11], detection of explosives [12,13], etc. Te THz generation has been observed upon ultrafast excitation of semiconductors, alloys, gas plasmas, and some material combinations including LiNbO 3 [14], ZnTe [15][16][17], GaAs [18], InAs [2,19], W/Co 40 Fe 40 B 20 /Pt [20][21][22][23], InGaN [24], and quantum wells (QWs) [25][26][27][28][29][30][31][32][33], to name a few. Te THz pulse generation is accomplished using various methods including photocurrent transients in gas plasmas, photocurrent surge from electro-optic materials [34][35][36][37][38], Cerenkov radiation in ferroelectric materials, diference frequency generation in nonlinear materials, spintronic emission from magnetic metal multilayers [23], and dynamic screening of electrostatic feld in QWs [25,27,29,30,32,33,…”

“…Te frst photon from an ultrafast laser source increases the overlap of the electron-hole wave function and absorption coefcient for the subsequent photon [58]. Te instantaneous absorption of the photon results in the spatial separation of wave functions and the creation of polarized electron-hole pairs in a time interval much shorter than the typical recombination time [31]. Te electric feld of such a dipole has a polarity opposite to the built-in piezoelectric feld.…”