  The layered van der Waals (vdW) material MnBi$_2$Te$_4$ is an intrinsic
magnetic topological insulator with various topological phases such as quantum
anomalous Hall effect (QAHE) and axion states. However, both the zero-field and
high-temperature QAHE are not easy to realize. It is theoretically proposed
that the exchange bias can be introduced in the MnBi2Te4/ferromagnetic (FM)
insulator heterostructures and thus opens the surface states gap, making it
easier to realize the zero-field or high-temperature QAHE. Here we report the
electrically tunable exchange bias in the van der Waals
MnBi$_2$Te$_4$/Cr$_2$Ge$_2$Te$_6$ heterostructure. The exchange bias emerges
over a critical magnetic field and reaches the maximum value near the magnetic
band gap. Moreover, the exchange bias was experienced by the antiferromagnetic
(AFM) MnBi$_2$Te$_4$ layer rather than the FM layer. Such van der Waals
heterostructure provides a promising platform to study the novel exchange bias
effect and explore the possible high-temperature QAHE.
