Study of non-equilibrium thermal transport in Ge2Sb2Te5 thin films under ultrafast laser excitation using a photo-excited carrier integrated semiconductor model

Abstract

A two-temperature semiconductor model was used to investigate the non-equilibrium thermal transport in Ge2Sb2Te5 thin films caused by an ultrashort laser pulse ranging from atto- to nanoseconds. In the model, photo-excited carriers were considered based on the semiconductor absorbing mechanism. As a general rule, shorter laser pulses led to shorter equilibration time between carrier and lattice systems. However, a minimum time to reach the thermal equilibrium (about 80 ps) was obtained for both the attosecond and femtosecond laser pulses, which was mainly determined by material properties instead of the pulse width. The carrier density had a strong influence on the temperatures of both the carrier and lattice systems, and photo-excited carriers played an important role in the first 40 ps under the attosecond and femtosecond laser irradiations. Besides, the ambipolar diffusion effect significantly reduced the density of free carriers and then extended the crystallization and amorphization times of Ge2Sb2Te5.

Evolution of quasiperiodic microstructure of Ge–Sb–Te-based films irradiated by multi-pulsed picosecond laser

“…Ps laser pulse can induce ultrafast photon ionization [33], generating a very high dense free carrier [34]. In our previous work, when the pulse width was 15 ps, the free carrier density reached its peak value of 2.1 × 10 21 cm −3 in ~35 ps, and then dropped quickly to zero after 80 ps [35]. The high dense free carriers impact and disturb the lattice, resulting in nonthermal melting [34].…”

Study on transient photocurrent induced by energy level defect of schottky diode irradiated by high power pulsed laser

“…The energy level concentration of the multi carrier defect is 2.8 × 10 13 /cm 2 . Generally speaking, when a short pulse laser irradiates a semiconductor material, a large number of nonequilibrium photogenerated carriers will be generated in a short time 19 . The Si-P material in this test is an N-type semiconductor, and its electrons are multi carriers, in which the minority carrier trap plays a role usually.…”