GaN-based　light　emitting　diodes　(LEDs)　with　InGaN　as　the　capping　layer　was　designed　in　our　experiment.　The　forward　voltage　at　the　typical　driving　current　of　20　mA　was　obviously　changed　by　adjusting　the　thickness　of　the　InGaN　layer.　We　were　concerned　with　the　effect　of　polarization　and　solved　the　concentration　and　the　tunneling　probability　of　the　two　dimensional　hole　in　the　triangular　potential　well　at　the　surface　InGaN/GaN　interface　and　obtained　the　minimal　for-ward　voltage.　The　calculation　results　were　consistent　with　the　experimental　data.