Role of Schottky Barrier Height Modulation on the Reverse Bias Current Behavior of MIS(p) Tunnel Diodes

Current and capacitance characteristics of Al/SiO
₂
/Si(p) metal-insulator-semiconductor tunnel diode (MISTD) with oxide thickness in the range of about 2–4 nm were fabricated and studied in detail in this work. We found that the saturation reverse bias current will increase with oxide thickness in this range of oxide thickness. This non-intuitive phenomenon is caused by different levels of Schottky barrier height modulation (SBHM), which leads to the injection of the majority from metal. The majority current of Al/SiO
₂
/Si(p) MISTD is usually neglected because of the blocking of the oxide layer and the Schottky barrier. The mechanism and numerical analysis of SBHM are discussed in this work. SBHM is significant when the oxide is thin enough for the majority to tunnel from metal to semiconductor and thick enough to hold a part of the minority inversion layer. In this specific oxide thickness range, increasing oxide thickness will increase the ability to hold the inversion layer, thus leading to higher oxide voltage (V
_ox
) and stronger SBHM. As a result, we find that stronger SBHM lets more majority have enough energy to inject from metal to semiconductor and cause higher reverse saturation current in MISTD with thicker oxide. With the numerical analysis in our work, we also predict this non-intuitive phenomenon will start to turn around when oxide thickness is thicker than about 33Å. This phenomenon indicated that majority current is an un-neglectable component when the oxide is thick enough to hold the inversion layer partially. The analysis in this work is also helpful to complete the missing part of the theory describing the current behavior of MISTD.