On an AlGaInP Light-Emitting Diode With a Modulation-Doped Multiquantum-Well (MD-MQW) Structure

An interesting AlGalnP multiquantum-well (MQW) light-emitting diode (LED) with an n-type modulation-doped (MD) structure, grown by low-pressure metal-organic vapor-phase epitaxy (LP-MOVPE), is fabricated and studied. This n-type MD-MQW LED exhibits lower dynamic resistance, higher luminescence, and higher luminous efficiency than those of a conventional undoped-MQW LED. Experimental results show a higher luminous efficiency of 16.05 lm/W and higher luminescence of 2.53 lm are obtained for the MD-MQW LED which are superior to the corresponding values of 14.49 lm/W and 2.04 lm for the undoped-MQW LED under dc operation. In addition, the n-type MD-MQW LED exhibits a higher quantum efficiency of 7.2% under dc operation as compared with the 6.7% of the undoped-MQW LED. The reduced junction temperature of 12degC at 200 mA is also acquired for the MD-MQW LED. Moreover, the brightness reliability of this new device is found to be comparable to the undoped-MQW LED. These positive results could be attributed to the presence of a higher electron concentration in the active region of the MD-MQW structure which causes the suppression of electron thermal velocity especially at a high level injection condition, and a reduced junction heating effect.