Ga

1-x

Al

x

As red DH LED shown in Fig.1 has been prepared.Compared with SH device its luminous flux has remarkably increased and reached 22mLm at 20mA.There is a stronger infrared peak at about 890 nm in EL spectrum besides a red main peak. It is found that the relative intensity of the infrared band to the red one is related to the luminous efficiency of devices.The stronger the infrared emission is

the poorer the efficiency(see Table 1). This implies that a part of injection energy is expended in generating the infrared emission which does not contribute to luminous flux. Therefore

to find out the origin of the infrared emission and then to eliminate it will raise the luminous efficiency of devices in the furture.