Charge Transport in Magnetic Semiconductor p-n Heterojunctions

Previously, the p-n-p bipolar magnetic junction transistor was demonstrated using a magnetic semiconductor InMnAs as the collector. A current gain beta(dc) as high as 20 of the transistor is observed at 300 K. A negative magnetoamplification of -150% is obtained when the applied magnetic field is 8 T. In order to assess the gain mechanism for such transistors, we measured the minority carrier lifetime in a p-n InMnAs/InAs heterojunction diode. A minority carrier lifetime of 320 ns was obtained at room temperature. For the p-n-p MJT, a decrease in the emitter injection efficiency with the magnetic field is observed for the various base currents, which is attributed to the positive magnetoresistance of the p-type InMnAs. The emitter injection efficiency decreases with the magnetic field leading to the observed negative magnetic amplification.