The third approach, which we adopt in this study, considers two types of heat sources: fast heat sources resulting from immediate photon-lattice interactions and nonradiative relaxation, and slow heat sources resulting from recombination of photogenerated carriers [18; 32; 33; 34]. Among these, the third approach--based on distinguishing fast and slow heat sources--is particularly well-suited for the PA analysis of moderately doped semiconductors. This model forms the theoretical basis of our study. The first type of heat source, referred to as the fast heat source, is characteristic of all solid-state materials. It originates from the interaction of the excitation electromagnetic radiation with lattice vibrations and non-radiative de-excitation processes. These mechanisms rapidly convert the absorbed photon energy into heat and operate on timescales much shorter than those relevant to photothermal detection. As a result, the temporal profile of this heat generation closely follows that of the incident optical pulse. However, due to the electronic band structure of semiconductors--which includes a filled valence band, a partially empty conduction band, and a band gap in between--photons with energy exceeding the band gap can excite electrons into the conduction band, leaving behind holes in the valence band [35]. These electron-hole pairs (quasi-free charge carriers), bound by Coulomb attraction, diffuse through the material driven by concentration gradients and eventually recombine after a characteristic time known as the carrier lifetime. During recombination, their kinetic energy is transferred to the lattice, generating additional heat. These recombination events are distributed in space and time, and form what is known as the slow heat source. The overall temperature distribution in the semiconductor is therefore a superposition of the contributions from fast and slow heat sources. This dual-source model is especially appropriate for moderately doped, narrow-band gap semiconductors, where the Fermi level remains within the band gap and the photoinduced plasma plays a significant role in thermal dynamics. From the perspective of PA research and device characterization, this approach provides a physically realistic and experimentally relevant description of how photogenerated carriers influence the PA signal. It links electronic properties, carrier dynamics, and recombination processes to the optically induced heating and the resulting acoustic response detectable in gas-microphone or other PA configurations [18; 32; 33; 34]. Using the third modeling approach, where photogenerated charge carriers contribute to additional heating via recombination (slow heat sources), frequency-domain PA measurements have already enabled the electronic characterization of semiconductors. However, despite having an original time-domain PA setup with gas microphones and validated knowledge from frequency-domain studies, the use of time-domain gas-microphone PA techniques for the electronic characterization of semiconductors remains challenging. The main obstacle lies in the complexity of the system's transfer characteristics in the time domain--specifically, the transformation of optically induced temperature variations on the non-illuminated surface into acoustic signals, and subsequently into the final electrical signal detected by the microphone. This transformation process is not yet fully understood [22; 36], and as a result, it is currently not possible to deconvolve the contributions of charge carrier dynamics from those of the detection system response with sufficient accuracy. Therefore, although our broader research goal is to establish time-domain PA methodologies for the electronic characterization of semiconductor structures, this cannot be realized without first addressing a fundamental intermediate step: quantifying the influence of photogenerated charge carriers on the transient temperature response at the non-illuminated surface.