【摘要】 用改进了的射频溅射仪,对InGaAsP/InP DH面发光管窗口沉积Al₂O₃抗反射层,以提高光功率的输出。本文采用了两种涂层途径,其一是对单个发光管窗口直接涂层,另一则是对发光管管芯片上窗口涂层,并对二者作了比较。更多还原

【Abstract】 LEDs for application in long-haul optical communication system are characterized by their high effective radiance and the long-term reliability. Although diodes having hemispheric or spheric lens on the emitting surface exhibit higher external efficiencies,but such devices are too expensive to make for this application purpose.Therefore in the present work, we investigated the effect of front facet sputtered A12O3 coating on light output increase of InGaAsP-InP LED.A conventional RF sputtering equipment with the source power 3kW at 13.5MC was used in deposition of A12O3 AR coating.A high purity A12O3 disk was employed, as target.The calulated results show that reflectivity of A12O3 AR coating on InP surface is very low. It’s coefficient of thermal expansion (α=6.8×10-6℃-1) is approximately comparable to that of InP (α= 4.5×10-8℃-1). In order to eliminate possible second electrons bombardment on devices during deposition of A12O3 coating. It is necessary to modify the sputtering equipment to provide a “region without damage” on the surface of the substrate table where diodes are placed for A12O3 coating.Fig. 1 shows the profile of the LED with relative reflective index variation.The experimental results for LEDs with and without AR coatings are given in Table 1. Which shows that light output, driven at a current of 100mA, is raised from 160-590 μW for all uncoated LEDs to 210-740μW for the same diodes coated with 1600-2240A A12O3 coatings. This corresponds to a light output increase of 22-43% or about 30% on an average.Fig.2 shows the typical light output as function of current density for a LED. Light output increases from 590μW for the uncoated diode to 740μWfor the same diodes coated 1650A A12O3.An additional coating method for increase light output of LEDs was applied. The LED ’s wafer was scribed apart into two portions, from a por- tion some LEDs were fabricated, and on front facets of the other portion A12O3 coating was deposited by sputtering. Then it was scribed apart and individual chip obtained, from which some LEDs with A12O3 coating on front facets were fabricated. Then, the optical power of two kinds of LEDs was measured for comparison.The light output and voltage drop as a function of drive current for the LEDs with -1700A coatings on front facets are given in Fig.3. Which shows the output at 100mA are as high as 0.8-1.23mW. The experimental results for two kinds of LEDs are given in Table 2 . Which shows that light output of chips with AR coating is more than that of chips without AR coating. Obviously, this coating method is rather simple and suitable for increase the light output of LEDs on a larger scale.In addition we also found that the near-field distribution of the LEDs was not changed appreciable after deposition of AR coating on the front facets.更多还原