Electric field modulation of electron spin transfer and relaxation in GaN/AlGaN heterostructures with two intrinsic processes

External electric field effects on spin relaxation dynamics in GaN/$\mathrm{A}{\mathrm{l}}_0.25\mathrm{G}{\mathrm{a}}_0.75\mathrm{N}$ heterostructures are investigated by time-resolved Kerr rotation spectroscopy. Two types of spin relaxation processes are distinguished by adjusting the excitation energy, characterized with a difference of about an order of magnitude in spin relaxation time. It is found that the electron spin transfer from the bulk GaN barrier to the triangular well occurs under the considerable built-in electric field at the GaN/AlGaN heterointerface. Significantly, a reverse bias voltage can remarkably decelerate the spin transfer process from the bulk electrons to the two-dimensional electrons gas (2DEG) by weakening the interfacial electric field, while a forward bias voltage would induce more serious spin scattering for the 2DEG leading to a short spin relaxation time of 10 ps. The electric-field controlled spin relaxation dynamics would pave a way for the development of GaN-based spintronic devices.