We applied the top-gate configuration to organic light-emitting transistors (OLETs) having an organic semiconductor crystal and an aluminumdoped zinc oxide (AZO) layer. The AZO layer was inserted between a quartz substrate and the organic crystal. The devices had the top-contact configuration where gold and an alloy of magnesium and silver were used for the contacts. Silver and Parylene C ® were used for a gate contact and a gate insulator for the top-gate configuration, respectively. These OLETs showed more efficient current injection at low voltages than both the devices without a gate contact and the devices having the bottom-gate configuration. The present results indicate that the top-gate configuration is effective for improving the crystal OLET characteristics.