Spin-dependent tunneling properties in GaMnAs-based magnetic tunnel transistors

III-V-based ferromagnetic-semiconductor heterostructures comprising GaMnAs are hopeful candidates for future spintronic devices. Thus far, only two-terminal devices have mainly been studied. Meanwhile, GaMnAs-based `three-terminal' magnetic tunnel transistors (MTTs) have a potential to add novel functions to integrated circuits. We prepared MTT structures composed of GaMnAs (30 nm)/ AlAs (2 nm)/ GaMnAs (30 nm)/ GaAs:Be (30 nm; 1*10$^{17}$cm$^{-3})$ on $p$-GaAs(001) substrates using molecular-beam epitaxy (MBE). The $V_{EB}$ dependence of $I_{C}$, $I_{E}$, and $I_{B}$ shows that the current transfer ratio \textit{$\alpha $} (= $I_{C }$/$ I_{E})$ is 0.8-0.95; this is much higher than 0.03, the maximum value reported in metal-based MTTs. The current gain \textit{$\beta $} (= $I_{C }$/$ I_{B})$ is of the order of 10, which means that GaMnAs-based MTTs have current amplifiability. The $V_{EC}$ dependence of the tunneling magnetoresistance (TMR) ratio differed significantly from that observed in single-barrier magnetic tunnel junctions (MTJs). This work was partly supported by PRESTO / SORST of JST, Grant-in-Aids for Scientific Research, IT-RR2002 of MEXT, and Kurata-Memorial Hitachi Sci. {\&} Tech. Foundation.