In this paper, drain current transient characteristics of β-Ga₂O₃ high electron mobility transistor (HEMT) are studied to access current collapse and recovery time due to dynamic population and de-population of deep level traps and interface traps. An approximately 10 min, and 1 h of recovery time to steady-state drain current value is measured under 1 ms of stress on the gate and drain electrodes due to iron (Fe)–doped β-Ga₂O₃ substrate and germanium (Ge)–doped β-Ga₂O₃ epitaxial layer respectively. On-state current lag is more severe due to widely reported defect trap E_C – 0.82 eV over E_C – 0.78 eV, -0.75 eV present in Iron (Fe)-doped β-Ga₂O₃ bulk crystals. A negligible amount of current degradation is observed in the latter case due to the trap level at E_C – 0.98 eV. It is found that occupancy of ionized trap density varied mostly under the gate and gate–source area. This investigation of reversible current collapse phenomenon and assessment of recovery time in β-Ga₂O₃ HEMT is carried out through 2D device simulations using appropriate velocity and charge transport models. This work can further help in the proper characterization of β-Ga₂O₃ devices to understand temporary and permanent device degradation.