Visible and NIR integrated Phototransistors in CMOS technology

In this paper we present several different types of fully integrated pnp phototransistors realized in a 0.6 μm OPTO ASIC CMOS process using low doped epitaxial starting wafers. Different types of phototransistors were realized by varying base doping profile and emitter area. This variations lead to different characteristics of the phototransistors. Devices with high responsivities or high bandwidths are achieved. Responsivities up to 98 A/W and 37.2 A/W for modulated light at 330 kHz were achieved at 675 nm and 850 nm wavelengths, respectively. On the other hand bandwidths up to 9.7 MHz and 14 MHz for 675 nm and 850 nm wavelength, respectively, were achieved at the expense of a reduced responsivity. Due to the fact that the used process is a standard silicon CMOS technology, low-cost integration to an integrated optoelectronic circuit is possible. This could lead to possible applications like low-cost, highly sensitive optical receivers, optical sensors, systems-on-a-chip for optical distance measurement or combined to an array even in a 3D camera.