GaN基微缩化发光二极管尺寸效应和阵列显示

GaN based micro-light-emitting diode size effect and array display

设计制备了不同大小的单颗微缩化发光二极管(Micro-LED)和Micro-LED阵列.其中,单颗Micro-LED尺寸为40-100μm,其电极结构为共N极,P极单独引出;阵列像素数量为8×8,被动驱动结构,像素大小为60μm.器件制备过程中使用厚光刻胶作掩膜,刻蚀N型GaN外延片至衬底,形成隔离槽.通过优化电极结构和厚度,提高了P电极在隔离槽爬坡处的可靠性;使用现场可编程门阵列(field-programmable gate array,FPGA)对Micro-LED被动阵列进行了驱动显示.对于不同尺寸的单颗Micro-LED进行了电学、光学、热学等方面的测试分析.结果表明:随着尺寸的减小,Micro-LED所能承受的电流密度越大;Micro-LED与普通蓝光LED相比具有较大的k系数,并且随着尺寸的减小,k系数的数值增大,热稳定性不如传统蓝光LED.FPGA可以实现对Micro-LED被动阵列的良好驱动.

Single micro-light emitting diodes(LEDs) with different sizes and array micro-LED are designed and prepared, where the sizes of the single micro-LEDs are in a range of 40-100 μm, their electrodes are all co-N electrodes, P electrode is drawn out alone;the number of array pixels is 8 × 8, which is a passively driving structure with a pixel size of 60 μm. In the process of device preparation, N electrode and P electrode are fabricated by the sputtering & stripping method. The electrode thickness is 2.4 μm. Thick photoresist 5120 is used as a mask, and N GaN is etched to the substrate by using the ICP dry etching to form an isolation trench.The PECVD technique is used to deposit an SiO2 insulating layer with a thickness of 10000 ?. By optimizing the electrode structure and thickness, the reliability of the P electrode at the slope of the isolation trench is improved, and the SiO2 insulating layer has good encapsulation;field programmable gate array(FPGA) is used to drive and display the micro-LED passive array. The single micro-LEDs of different sizes are tested and analyzed in the aspects of electrics, photics and thermotics and the results of which show that the current density corresponding to the peak radiation flux of 80 μm micro-LED is 1869.2 A/cm2, which is 57.1% higher than that of 100 μm micro-LED, indicating that the current density corresponding to the peak radiation flux of micro-LED increases as the size decreases;compared with the ordinary blue LED, the micro-LED has a large k factor, and with the size decreases, the value of the k factor increases, indicating that the micro-LED series resistance is larger, and the thermal stability is not so good as the traditional blue LED. Finally, the field programmable gate array(FPGA) can achieve a good drive for the micro-LED passive array. The driving principle is passive scanning driving, which is carried out in a row-by-row lighting mode. The FPGA clock is 50 MHz,and 320 ns is required for the circuit to scan all rows.