Effect of top distributed Bragg reflectors on the performance of 650 nm AlGaInP resonant cavity light-emitting diodes

Abstract

Three kinds of 650 nm AlGaInP resonant cavity light-emitting diodes (RCLEDs) are fabricated by metal organic chemical vapor deposition (MOCVD) with different numbers of pairs of top distributed Bragg reflectors (DBRs), which are 15, 10 and 5, respectively. By comparing the full width at half maximum (FWHM), light power and the angular far-field emission of the devices, the device with 15 pairs of top DBRs shows the best performance. Its FWHM is 13.4 nm and the light power is 0.63 mW at a driving current of 30 mA.The resonant cavity light-emitting diode (RCLED) proposed by Schubert et al. [1] is a good choice between LED and LD. Because it has a narrower spectrum and better directionality than LED, and is cheaper than LD, RCLED has attracted much attention in recent years [2,3] . The RCLED consists of a top reflective mirror, a bottom reflective mirror and a cavity with active layers. The distributed Bragg reflector (DBR) is usually used as the reflective mirror. The reflectivity of the bottom DBR is designed as high as possible, even up to approximate 100%, while the top one can be designed according to the device requirements [4,5] . Thus, the top DBR has a significant impact on the characteristics of RCLED, such as the emission spectrum, the output light power and the optical field distribution.In this letter, we study the effect of the top DBR pairs on RCLED device performance. Three samples of 650 nm RCLED which have different pair numbers of top DBRs are fabricated by means of metal organic chemical vapor deposition (MOCVD). The results show that the device with 15 pairs of top DBRs shows the best performance.As shown in Fig.1, the epitaxy structure of RCLED is fabricated by MOCVD on the 2 inch n + -type GaAs substrate. At first, 34 pairs of AlAs-Al 0.5 Ga 0.5 As bottom DBR layers grow on the GaAs buffer, and then the active layer grows, including three 5 nm wide compressive strain Ga 0.5 In 0.5 P-(Al 0.5 Ga 0.5 ) 0.5 In 0.5 P multiple quantum wells (MQWs). After the growth of (Al 0.3 Ga 0.7 ) 0.5 In 0.5 P-Al 0.5 In 0.5 P top DBR layers, Mg-doped p-type GaP is deposited as window layers. After the epitaxial growth, p-type AuZnAu top electrode and ntype AuGeNi bottom electrode are formed. Finally, the chips are cutting into the size of 300 m 300 m for device testing.In order to study the influence of top DBRs on RCLED characteristics, 3 samples are made, in which all the other structure parameters are the same, except that the pair number of top DBRs in sample#1 is 15, sample#2 is 10, and sample#3 is 5.The spectrum and optical field distribution of samples are tested by the PMS-50 spectroscope and LED620 light intensity tester (Everfine), and the output light power is measured in an integrating sphere.