•A two-step Au deposition improved the reflectivity while retaining the low resistivity is demonstrated.•The AuGeNi/Au(1)/Au(2) (70 nm/30 nm/100 nm) Ohmic contact to N-AlGaAs with a low resistivity of 4.65 × 10−6 Ω·cm2 and a high reflectivity of 93.11 % at 850 nm have been obtained after RTP 420 °C for 1 min.•The LOP of IRLED with AuGeNi/Au(1)/Au(2)/Cu (70 nm/30 nm/100 nm/45 μm)composite metal substrate is 89.2 % higher than that of GaAs substrate at 300mA current. Substrate transfer technology is a common way to prepare high-power infrared light emitting diode (IRLED), which seriously affects the photoelectric performance and reliability of LED. In this paper, a preparation technology of LED with composite metal substrate is presented. Based on electroplating and electron beam evaporation, AuGeNi/Au(1)/Au(2)/Cu composite metal substrate with thickness of 70 nm/30 nm/100 nm/45 μm was prepared, and low resistivity of 4.65 × 10−6 Ω⋅cm2 and high reflectance of 91.3 % were obtained. Compared with the original GaAs substrate, the light output power (LOP) of electroluminescence is increased by 89.2 % at the current of 300 mA.