The effect of the AlGaN electron blocking layer (EBL) thickness on the electrical and optical properties of 310 nm AlGaN single quantum well (SQW) light-emitting diodes (LEDs) has been investigated. A large ideality factor extracted from the current-voltage (I-V) characteristics indicates that a tunneling mechanism dominates the carrier transport process in the LEDs. The ideality factor decreases with increasing EBL thickness suggesting that deep-level state assisted tunneling is reduced. In addition, the QW emission intensity is enhanced with the introduction of an EBL due to the reduction of electron overflow to the p-type layer. The QW emission intensity is sensitive to the EBL thickness. This is attributed to the reduction of electron tunneling to the p-type layer with an EBL. (C) 2009 Elsevier B.V. All rights reserved.