Demonstration of a graphene-base heterojunction transistor with saturated output current

Abstract

A novel transistor with a graphene base embedded between two n-type silicon emitter and collector layers (graphene-base heterojunction transistor) is fabricated and characterized electrically. The base voltage controlled current of the device flows vertically from the emitter via graphene to the collector. Due to the extremely short transit time for electrons passing the ultimately thin graphene base, the device has a large potential for high-frequency RF applications. The transistor exhibits saturated output currents and a clear modulation of the collector current by means of the graphene base voltage. The vertical transfer current from the emitter via the graphene base to the collector is much lower than expected from device simulations. A comparison of the graphene-base transistor and a reference silicon n-p-n bipolar transistor is performed with respect to the main DC transistor characteristics. A common-emitter gain of larger than one has been achieved for the reference device while the graphene-base transistor so far exhibits a much lower gain.

Improved graphene-base heterojunction transistor with different collector semiconductors for high-frequency applications

“…The collector current of the device is saturated for increased Vce values. Compared to the previous device generation [5], the output current (Jc) and the common-emitter current gain (Jc/Jb) of the GBHT could be increased by about one order of magnitude. This was achieved through optimized cleaning of the graphene surface before the n-a-Si:H deposition.…”

“…This configuration also led to device instabilities as the a-Si:H/graphene diode tends to breakthrough when biased with increased reverse voltages. J c V cb = 0 V For comparison, a reference transistor with a p-type silicon base was also fabricated and characterized [5]. A much higher output current (Jc ≈ 5x10 -1 A/cm² at Vbe = 1 V) is achieved for the reference silicon NPN transistor compared to the GBHT (7x10 -4 A/cm² at Vbe = 8V).…”

“…First attempts were made recently to put the GBHT into practice by means of amorphous silicon emitter and collector layers or crystalline silicon collector layers [4,5]. In this study, improved device performance with increased output current and common-emitter current gain are demonstrated.…”

“…wet chemical transfer approach [5]. On top of the graphene monolayer, a 100 nm thick n-type amorphous silicon layer was deposited by VHF-PECVD (140 MHz) using a shadow mask.…”

N‐Doped and P‐Doped Graphene on MgO (111): A First‐Principles Study

“…Graphene is a honeycomb crystal structure with sp 2 hybridization, it has been applied in many fields due to its excellent electrical, thermal, optical, and mechanical properties, [1][2][3] especially in transistor devices. [4,5] There are many methods for preparing graphene films, and chemical vapor deposition (CVD) is highly respected in laboratories and industry for its ability to synthesis large-area, high-quality graphene films. [6] The traditional CVD method to prepare graphene films requires a metal substrate as a catalyst, such as Ni [7] and Cu.…”