An interesting AlGaInP multiple quantum well light emitting diode (LED) with a thin carbon-doped (C-doped) GaP contact layer and a transparent conducting indium tin oxide (ITO) film is fabricated. Moreover, LEDs with different contact layer structures are presented and compared in this work. The experimental results illustrate that the LED with a C-doped GaP contact layer exhibits a higher output power of 31.4 mW and a higher external quantum efficiency of 9%. The light output power, under dc 20 mA operation, of this LED is increased by a factor of 18% compared with conventional LEDs without the C-doped contact and ITO spreading layers. These results are mainly attributed to the improved contact property and lower optical absorption effect. In addition, the studied device shows the lower dynamic resistance (5.1 @20 mA), reduced leakage current (1.5x10(-9) A@-5 V), reduced wavelength shift (with 1.7 nm variation between 10 and 200 mA), and lower thermal-induced optical degradation (< 0.3% during 50 mA, 220 h aging test). Therefore, the studied device shows promise in fabricating high performance AlGaInP LEDs.