Simple Harish-Chandra bimodules in positive characteristics

Let $G$ be a standard reductive group over an algebraically closed field of positive characteristic and let $\mathfrak{g} = \operatorname{Lie}(G)$. The category of Harish-Chandra bimodules consists of $G$-equivariant $U(\mathfrak{g})$-bimodules such that the adjoint $\mathfrak{g}$-action integrates