Superinjection in Diamond p - i - n Diodes: Bright Single-Photon Electroluminescence of Color Centers Beyond the Doping Limit

Abstract

Efficient generation of single photons on demand at a high repetition rate is a key to the practical realization of quantum-communication networks and optical quantum computations. Color centers in diamond and related wide-bandgap semiconductors are considered to be the most promising candidates for building such single-photon sources owing to the outstanding emission properties at room temperature. However, efficient electrical excitation of color centers in most materials remains a challenge due to the inability to create a high density of free carriers. Here, we predict a superinjection effect in diamond p-i-n diodes. By employing a comprehensive theoretical approach, we numerically demonstrate that one can overcome the doping problem in diamond and inject four orders of magnitude more electrons into the i-region of the diamond p-in diode than the doping of the n-region allows. This high density of free electrons can be efficiently used to boost the single-photon electroluminescence process and enhance the brightness of the diamond single-photon source by more than three orders of magnitude.Moreover, we show that such a high single-photon emission rate can be achieved at exceptionally low injection current densities of only 0.001 A/mm 2 , which creates the backbone for the development of low-power and cost-efficient diamond quantum optoelectronic devices for quantum information technologies.

Bright Single-Photon Emitting Diodes Based on the Silicon-Vacancy Center in AlN/Diamond Heterostructures

“…The high density of injected carriers gives the possibility to achieve ultrahigh SPEL rate at moderate injection currents (Figure 4e). We find that the maximum SPEL rate is roughly five times higher than in diamond SPEDs based on p-i-n structures that exploit the superinjection effects [10,11]. For a single SiV center in diamond, the SPEL rate is equal to 2.9 × 10 6 cps at a current density at the top contact of 50 A/cm 2 and is as high as 3.9 × 10 6 cps at 500 A/cm 2 .…”

“…The activation energy of donors and acceptors in these materials is very high, which, combined with a nonzero compensation of donors (acceptors) by acceptor-type (donor-type) impurities and defects, results in a very low density of free carriers, which can be up to ten orders of magnitude lower than the doping density. In particular, the density of free electrons in n-type diamond is limited to about 10 11 cm −3 [10][11][12][13], which is much lower than the typical density of holes in p-type diamond (>10 14 cm −3 ) (Figure 2a). In turn, the single-photon electroluminescence (SPEL) rate of a single color center in the steady state is given by [14] SPEL r n r s r nr n p nr r…”

“…Recent theoretical findings show that it is possible to overcome the limitation on the SPEL rate imposed by the doping of n-type diamond using the superinjection effect in homojunction diamond diodes [10,11,19]. By exploiting this effect, one can inject up to four orders of magnitude more electrons into the i-region of the diamond p-i-n diode than the doping of the n-type region allows.…”

“…The doping density of the p-type diamond substrate is 10 18 cm −3 at a donor compensation ratio of 1%, which is typical for p-type diamond samples [18]. Free-carrier effective masses, electron and hole mobilities and other material parameters of diamond and AlN important for the operation of the SPED can be found in References [10,21]. The AlN layer plays a role of electron injection layer.…”

“…It is known for polarized emission at a wavelength of about 738 nm from the single negatively charged state, which features a narrow spectrum, large Debye-Waller factor at room and even high temperatures [5][6][7][8]. However, efficient electrical excitation of the SiV centers, as well as other color centers in diamond, is very challenging due to the inability to create a high density of free carriers, which is essential for bright single-photon electroluminescence [9,10] (Figure 1b). The reason for this is that wide-bandgap semiconductors, such as diamond, are the materials at the interface between semiconductors and insulators.…”