We successfully grew In-rich InGaN/GaN multi-quantum well (MQW) structures using growth interruption (GI) by metal-organic chemical vapor deposition (MOCVD). The quality of overgrown InGaN/GaN QW layer in MQWs was largely affected by the crystalline quality and interfacial abruptness of underlying QW layer. Introduction of 10 sec GI was very effective in improving the crystalline quality and interfacial abruptness of InGaN QW layer, and we successfully grew 10 periods of In-rich InGaN/GaN MQW with 10 sec GI and obtained very strong near-ultraviolet (UV) emission (~390 nm) at room temperature. We believe that use of ultra-thin In-rich InGaN QW layer can be a new candidate for near-UV source, which might replace the conventional low-indium content (<10%), thicker InGaN QW layer.[1] Time-resolved PL measurement of the ultra-thin In-rich InGaN/GaN MQWs showed that the radiative lifetime was 1.75 ns and that the peak position as well as the lifetime did not change with changes in pump power, suggesting that there is negligible piezoelectric effect and it is highly efficient in capturing carriers.

By adoting a two-step growth method during the growth of InGaN quantum well (QW) layer, we obtained strong near-UV (~400 nm) as well as blue (~450 nm) emissions at room temperature from 1-nm-thick In-rich InGaN/GaN MQW structures. Temperature-dependent photoluminescence and high-resolution transmission electron microscopy study show that the 400 nm peak is attributed to band-to-band transition in 1-nm-thick InGaN QW, whereas the 450 nm peak is attributed to localized centers induced by the second-step InN growth and growth interruption. The thermal stability of the 450 nm peak is much better than that of the 400 nm peak. Detailed optical properties of the In-rich InGaN/GaN MQWs will be reported.

[1] S.-Y. Kwon, S.-I. Baik, Y.-W. Kim, H. J. Kim, D.-S. Ko, E. Yoon, J.-W. Yoon, H. Cheong, and Y.-S. Park, Appl. Phys. Lett. 86, 192105 (2005).

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