OLED-on-CMOS integration for optoelectronic sensor applications

Abstract

Highly-efficient, low-voltage organic light emitting diodes (OLEDs) are well suitable for post-processing integration onto the top metal layer of CMOS devices. This has been proven for OLED microdisplays so far. Moreover, OLEDon-CMOS technology may also be excellently suitable for various optoelectronic sensor applications by combining highly efficient emitters, use of low-cost materials and cost-effective manufacturing together with silicon-inherent photodetectors and CMOS circuitry. The use of OLEDs on CMOS substrates requires a top-emitting, low-voltage and highly efficient OLED structure. By reducing the operating voltage for the OLED below 5V, the costs for the CMOS process can be reduced, because a process without high-voltage option can be used. Red, orange, white, green and blue OLED-stacks with doped charge transport layers were prepared on different dualmetal layer CMOS test substrates without active transistor area. Afterwards, the different devices were measured and compared with respect to their performance (current, luminance, voltage, luminance dependence on viewing angle, optical outcoupling etc.). Low operating voltages of 2.4V at 100cd/m2 for the red p-i-n type phosphorescent emitting OLED stack, 2.5V at 100cd/m2 for the orange phosphorescent emitting OLED stack and 3.2V at 100cd/m2 for the white fluorescent emitting OLED have been achieved here. Therefore, those OLED stacks are suitable for use in a CMOS process even within a regular 5V process option. Moreover, the operating voltage achieved so far is expected to be reduced further when using different top electrode materials. Integrating such OLEDs on a CMOS-substrate provide a preferable choice for silicon-based optical Microsystems targeted towards optoelectronic sensor applications, as there are integrated light barriers, optocouplers, or lab-onchip devices

Realization of 10 GHz minus 30dB on-chip micro-optical links with Si-Ge RF bi-polar technology

“…These ranges from Silicon forward bias p-n LED devices that operate at near 1μm wavelength region 23 to avalanche based Si LED devices that operate in the visible 450-750nm visible range 20,22,23, to organic light emitting diode (OLED) structures 24,25,26 into CMOS technology and which also emit light in the visible range 27 .…”

“…We evaluated some key optical characteristics of various available Si based optical sources in Fig 1. A number of viable optical light emitters have been developed in the nineties that have already been integrated with ease into mainstream silicon CMOS technology 18,22,27 . These ranges from Silicon forward bias p-n LED devices that operate at near 1μm wavelength region 23 to avalanche based Si LED devices that operate in the visible 450-750nm visible range 20,22,23, to organic light emitting diode (OLED) structures 24,25,26 into CMOS technology and which also emit light in the visible range 27 .…”

Optoelectronic chips integrate emitters and sensors

“…These operating voltages are inferior to the ones we reported last year. 3 One reason might be the roughness of the top metal layer.…”

Integrating Micro-Photonic Systems and MOEMS into Standard Silicon CMOS Integrated Circuitry

“…The Ge-Si heterostructure can be realized in Si-Ge CMOS processes, but increases complexity and costs. Organic based Light Emitting Diodes (OLED) utilize the sandwiching of organic layers between doped silicon semiconductor layers with high yields between 450 and 650 nm (Vogel et al , 2007). In spite, the incorporation of foreign organic materials through postprocesses this technology is a viable option.…”

“…Both standard CMOS as well as Silicon-on-Insulator (SOI) technology are suitable to realise some of the concepts. (Green et al, 2001;Kramer et al 1993;Hirschman et al 1996); avalanche based Si LEDs which operate in the visible from 450 -650 nm (Brummer et al, 1993;Kramer et al 1993;Snyman et 1996Snyman et -2006; organic light emitting diodes (OLED) incorporated into CMOS structures which also emit in the visible (Vogel et al, 2007); to, strained layer Ge-on-ilicon structures radiating at 1560 nm (Lui, 2010). Fig.…”