Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility¶
Why this mattered¶
This paper mattered because it established black phosphorus as more than a bulk layered material: it framed its atomically thin limit, phosphorene, as a serious member of the post-graphene two-dimensional semiconductor family. At the time, graphene had exceptional mobility but no native band gap, while MoS₂ offered a useful gap but generally lower room-temperature mobility and predominantly n-type behavior. Liu and coauthors showed that few-layer phosphorene could occupy a distinct and important middle ground: a mechanically exfoliable 2D material with an intrinsic, thickness-tunable direct band gap, strong in-plane anisotropy, and p-type transistor behavior with comparatively high hole mobility.
The paradigm shift was not just the identification of another 2D crystal. The paper made plausible a new design space for 2D electronics and optoelectronics in which band gap, carrier type, mobility, and crystallographic direction could all be engineered within an atomically thin semiconductor. Its field-effect transistor results, visible photoluminescence from the monolayer, and demonstration of a phosphorene PMOS / MoS₂ NMOS inverter connected the material’s calculated electronic structure to device-level possibilities. In doing so, it helped move 2D materials research beyond the graphene-versus-MoS₂ comparison toward a broader search for layered semiconductors with complementary transport polarity and tunable optical response.
Subsequent work on phosphorene and black phosphorus built directly on these possibilities: anisotropic transport, infrared-to-visible thickness-dependent optoelectronics, strain- and layer-controlled band structures, and van der Waals heterostructures. The material’s environmental instability later became a central limitation and research theme, motivating encapsulation, passivation, and device-engineering strategies. Even where phosphorene did not become a drop-in transistor platform, the paper’s influence was lasting: it showed that unexplored layered crystals could combine band gaps, mobility, polarity, and anisotropy in ways unavailable to the first wave of 2D materials, expanding the conceptual map for semiconductor materials discovery.
Abstract¶
We introduce the 2D counterpart of layered black phosphorus, which we call phosphorene, as an unexplored p-type semiconducting material. Same as graphene and MoS2, single-layer phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct, and appreciable band gap. Our ab initio calculations indicate that the band gap is direct, depends on the number of layers and the in-layer strain, and is significantly larger than the bulk value of 0.31-0.36 eV. The observed photoluminescence peak of single-layer phosphorene in the visible optical range confirms that the band gap is larger than that of the bulk system. Our transport studies indicate a hole mobility that reflects the structural anisotropy of phosphorene and complements n-type MoS2. At room temperature, our few-layer phosphorene field-effect transistors with 1.0 μm channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm(2)/V·s, and an on/off ratio of up to 10(4). We demonstrate the possibility of phosphorene integration by constructing a 2D CMOS inverter consisting of phosphorene PMOS and MoS2 NMOS transistors.
Related¶
- cite → Generalized Gradient Approximation Made Simple — The phosphorene study uses the PBE generalized-gradient approximation as a density-functional method for calculating black phosphorus electronic structure.
- cite → Atomically Thin
- cite → Single-layer MoS2 transistors — The phosphorene work cites single-layer MoS2 transistors as evidence that two-dimensional semiconductors can function in field-effect transistor devices.
- cite → Special points for Brillouin-zone integrations — The phosphorene calculations use Monkhorst-Pack special k-points to sample the Brillouin zone in density-functional simulations.
- cite → Efficient pseudopotentials for plane-wave calculations — The phosphorene simulations rely on Vanderbilt ultrasoft pseudopotentials to make plane-wave electronic-structure calculations computationally efficient.
- cite → Hybrid functionals based on a screened Coulomb potential — The phosphorene study uses the screened hybrid HSE functional to obtain improved band-gap estimates beyond semilocal density-functional theory.
- cite → Emerging Photoluminescence in Monolayer MoS2 — The phosphorene paper cites emerging photoluminescence in monolayer MoS2 as evidence that dimensional reduction can create optically active two-dimensional semiconductors.
- cite → Experimental observation of the quantum Hall effect and Berry's phase in graphene — The phosphorene paper cites graphene's quantum Hall effect and Berry phase as a landmark demonstration of novel charge transport in two-dimensional crystals.
- cite → Two-dimensional gas of massless Dirac fermions in graphene — The phosphorene paper cites graphene's massless Dirac fermions as the archetype motivating searches for other atomically thin materials with distinctive electronic bands.
- enables ← Generalized Gradient Approximation Made Simple — The PBE generalized-gradient approximation enabled first-principles calculations of phosphorene band structure and carrier mobility.
- enables ← Special points for Brillouin-zone integrations — Monkhorst-Pack special k-points enabled accurate Brillouin-zone sampling in the density-functional calculations of phosphorene.
- enables ← Efficient pseudopotentials for plane-wave calculations — Efficient plane-wave pseudopotentials enabled tractable density-functional simulations of phosphorene's atomic and electronic structure.
- enables ← Hybrid functionals based on a screened Coulomb potential — The screened hybrid HSE functional enabled more accurate phosphorene band-gap calculations than semilocal density functionals.
- enables ← Experimental observation of the quantum Hall effect and Berry's phase in graphene — Graphene's quantum Hall and Berry-phase results established 2D crystals as hosts of distinctive quantum electronic behavior, motivating analogous studies in phosphorene.
- enables ← Two-dimensional gas of massless Dirac fermions in graphene — Graphene established experimentally accessible 2D Dirac-material physics, motivating the search for other atomically thin crystals such as phosphorene with distinct band gaps and mobility.