Multiphoton photocurrent in wide bandgap semiconductors for nonlinear optoelectronics: Comparison of GaP, GaN/InGaN, and SiC

Abstract

Wide bandgap semiconductors are ideally suited for nonlinear optoelectronics. Because their bandgaps are larger than 2 eV, simultaneous absorption of two or more near-infrared photons is necessary to excite the electrons from the valence to the conduction band. Understanding of the processes that affect multiphoton absorption is important in the design and fabrication of optoelectronic devices. Here, we present an overview of the photocurrent response in photodetectors made from GaP, GaN, InGaN, and SiC when they are excited by photons at 1.2 eV. Recent measurements have shown that sub-bandgap absorptions contribute to photocurrent in GaP, and, thus, it is not a good material for nonlinear optoelectronics. Similarly, the response of GaN is affected by long-lived trapped charges. Photocurrents in InGaN and SiC are predominantly from three- and four-photon absorption, respectively. Moreover, these materials can withstand excitation intensities higher than 1011 W cm−2, making them appropriate platforms for nonlinear optoelectronics.

Probing Silicon Carbide with Phase-Modulated Femtosecond Laser Pulses: Insights into Multiphoton Photocurrent

“…If only N -photon absorption has a significant contribution to the measured signal, then the amplitudes of the signals at all harmonics scale with the N th power of the average intensity. On the other hand, if different orders of MPA contribute, the scaling of the signals at different modulation frequencies will be different, based on which one can identify the pathways of related MPA. , …”

“…The order of MPA depends on the material’s electronic structure. For example, it has been found that one-, two-, and three-photon absorptions contribute to photocurrent in gallium phosphide (GaP)-based photodetectors while only three-photon absorption contributes in indium gallium nitride (InGaN) photodetectors. − …”