Controlled Generation of a p–n Junction in a Waveguide Integrated Graphene Photodetector

Abstract

Photodetectors convert light into electrical signals and are at the heart of any optical link. In silicon photonics, traditionally germanium (Ge) [1,2] or III-V compound semiconductors [3,4] are used for photodetection and both technologies have reached a high level of maturity. Nevertheless, the direct monolithic integration of III-V photodetectors on Si wafers remains a challenge because of the large lattice constant mismatch and different thermal coefficients. Ge can be directly grown on crystalline Si, but pushing the bandwidth of Ge photodetectors to higher and higher frequencies [5,6,7] becomes increasingly difficult because of the material's poor electrical quality. One of the most promising routes to a new era of chip performance is the monolithic 3D integration of electronic and photonic components on the same chip, where a promising material for the photonic layers is SiN [8]. On these amorphous SiN layers, crystalline Ge (the prerequisite for realizing high

Graphene photodetectors with a bandwidth >76 GHz fabricated in a 6″ wafer process line

“…The sensitivity of a typical detector with a resistance of 130 Ω and a bias voltage of 1V was 1 mA/W (0.13 V/W). This sensitivity was approximately one order of magnitude above the value reported by Freitag et al for graphene flakes in a normal incidence setup, mainly due to the significantly increased absorption of light in our waveguide configuration [9].In order to determine the performance at high frequencies, a heterodyne setup according to the schematic shown in the supporting information of reference [16] was used. The optical radio frequency signal was generated by the superposition of two optical signals around 1550 nm, where one laser source was held at a constant wavelength and the other laser was tuned to generate the desired beating frequency.…”

“…The possible monolithic integration on various substrates that are not necessarily crystalline is a key merit that distinguishes graphene from Ge or III/V materials. The bandwidth reported for graphene photodetectors of up to 65 GHz [16] and sensitivity around 0.4 A/W without bias and 1 A/W with bias [22] underline the potential of graphene for chip integrated photodetectors. Besides an excellent device performance the integration in a large scale production environment is essential.…”

“…In order to determine the performance at high frequencies, a heterodyne setup according to the schematic shown in the supporting information of reference [16] was used. The optical radio frequency signal was generated by the superposition of two optical signals around 1550 nm, where one laser source was held at a constant wavelength and the other laser was tuned to generate the desired beating frequency.…”

“…The electronic and optic properties of graphene [4], the two dimensional allotrope of carbon, were studied extensively in the last years [5][6][7][8][9]. Moreover, competitive chipintegrated electro-optical devices like electro-optical modulators [10,11], efficient waveguide heaters [12] and ultrafast photodetectors [13][14][15][16] were fabricated using graphene as active material. The performance of graphene photodetectors on integrated silicon waveguides in terms of speed and sensitivity has improved significantly in the last years and the gap between the performance of graphene and competing technologies is vanishing [17][18][19][20][21].…”

Monolithic optoelectronic integrated broadband optical receiver with graphene photodetectors

“…With zero bandgap, graphene can absorb electromagnetic radiation ranging from far-infrared to UV light [25]. Graphene can fast respond to incident illumination [26][27][28] due to the ultrahigh carrier mobility (about 200,000 cm 2 V −1 s −1 in experiment [29]). Therefore, graphene has been considered as an outstanding material for PDs.…”