Electrical characteristics of n‐type diamond Schottky diodes and metal/diamond interfaces

Abstract

Electrical characteristics of n‐type diamond Schottky diodes and metal/diamond interfaces have been systematically investigated for phosphorus (P)‐doped homoepitaxial diamond layers. The current–voltage (I–V) characteristics of the Ni/n‐type diamond Schottky diode show excellent rectification properties from 297 K to 773 K. The ideality factor and the rectification ratio were 1.0 and ∼106 at +10 V at 573 K, respectively. The rectifying properties deteriorated with increasing P concentration in the diamond layers. Temperature‐dependent capacitance–frequency (C–f) and conductance–frequency (G–f) measurements on the Schottky diodes have shown that the capacitance is reduced at high frequency due to the inability of deep centers to maintain an equilibrium ionization state under a high‐frequency modulation. C–V measurements deduced that the P electrical activity (the ratio of the net donor concentration to the P concentration) was nearly 1 from low concentration (1.6 × 1016cm–3) to high concentration (2.7 × 1018cm–3) of P. The Schottky barrier height was found to be almost constant at ∼4.3 eV independent of the metal work function (Ni, Pt, Al and Ti). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Potential profile evaluation of a diamond lateral p–n junction diode using Kelvin probe force microscopy

“…Thus, the E F ÀE V of the oxidized n þ -layer becomes 4.3 eV, or the band bending of it 3.7 eV. Taking into account the strong Fermi-level pinning on oxidized surfaces and/or on n-type surfaces as discussed in literatures, our observation on the surface potential difference of 0.4 eV seems to be reasonable [17][18][19][20]. Figure 7 shows the KPFM results for the dynamic state, which has an applied voltage at the right-side electrode, while the left-side electrode is grounded.…”

“…In the present study, a hot acid mixture was used to obtain the oxidized surface. Typically, this type of surface exhibits strong pinning states at interfaces with any types of metals [16,17]. Therefore, the present method did not achieve complete oxidation, which resulted in large band bending.…”

Device Design of Diamond Schottky-pn Diode for Low-Loss Power Electronics

“…On the other hand, electrons in the Schottky metal cannot either diffuse or be injected into the n-type layer owing to the high B of $4:3{4:5 eV. 7,8) These findings indicate that the diamond SPND is a unipolar device. Thus, its switching speed can be expected to be as high as that of SBDs.…”

“…Here, 13,14) and B ' 4:3{4:5 eV. 7,8) In the free-hole distribution in Fig. 2(b), the free-hole distribution in the n-type layer is proportional to x À1=2 ; that is, this indicates a space-chargelimited current distribution, as described in x4.…”

“…Thus, when we apply the excellent properties of diamond to the low-loss high-power switching devices, the fabrication of a diode structure, which meets these conditions, can be a key technology. [1][2][3][4][5][6][7][8][9][10][11][12] After achieving n-type diamond by phosphorus (P) doping in 1997 for (111) surfaces 13) and in 2005 for (001) surfaces, 14) the research concerning diamond pn junctions [10][11][12] has been performed subsequently. [1][2][3][4][5][6][7][8] However, owing to the deep phosphorus donor level (the ionization energy for phosphorus donors, E D , is 570 meV), 13,14) the resistivity of the n-type layer is still high (10 5 -10 6 cm at a phosphorus concentration of $10 18 cm À3 ).…”