DESIGN AND FABRICATION OF ALGAINP LED ARRAY WITH INTEGRATED GAAS DECODE CIRCUITS

A two-dimensional (2-D) AlGaInP light-emitting diode (LED) array with monolithic integration of one-to-four GaAs MESFET decode circuits has been developed as an image source for portable virtual displays. The e pitaxial layers of AlGaInP LED's with light emission at a wavelength o f 605 mn were grown on a semi-insulating GaAs substrate by organometal lic vapor phase epitaxy, LED arrays consisting of 240 columns and 144 rows for a total of 34560 pixels were then fabricated on such epitaxia l wafers. One-to-four GaAs MESFET decode circuits consisting of eight MESFET's for each decode circuit and a total of 768 MESFET's for a 34 K decode array were fabricated on the semi-insulating GaAs substrate w ith removal of LED epitaxial layers around the periphery of the LED ar ray, LED arrays with the integrated decode circuits provide a great re duction in I/O terminals. The I/O count of the demonstrated 34 K decod e LED array is 104, which is much less than 384 for a comparable array without the integrated decode circuits. The pixel pitch of the LED ar ray is 20 mu m and each LED pixel has 10 x 10 mu m(2) emitting area. T he output power of LED pixel is 50 nW at an operation current of 50 mu A, The MESFET with a gate length of 1 mu m and a gate width of 200 mu m has a threshold voltage of -2.0 V and a maximum drain current of 40 mA at V-ds of 3 V, The address voltages used to activate the column d ecode circuits are 3 V for high and -3 V for low, while the address vo ltages used to activate the row decode circuits are 0 V for high and - 3 V for low. The operating voltage of the decode LED array ranges from 3 to 5 V, and the total power dissipation of the decode LED array is less than 16 mW.