Bright Visible Light Extraction from Amorphous Silicon Nitride Heterojunction Pin Diode

SEM, EDX spectroscopy and real-time optical microscopy of electroformed silicon nitride-based light emitting memory device

“…Since the EL efficiency of the LEDs increased significantly after electroforming, the phenomenon (or phenomena) that occurred during electroforming and caused the removal of the ITO from the structure may be expected to have led to similar changes in the Si-based thin films. In our previous model [4,8], we suggested that structural changes occurring during electroforming, leading to enhanced EL efficiency, might have been caused by Joule heating. It was shown previously [8] that ITO, which was coated by physical vapor deposition at room temperature, crystallizes at high local temperature caused by the Joule effect during electroforming.…”

“…However, surface roughening may be related also to the nanocrystallization of the Si-based films. It is well known that dehydrogenation of a-Si:H structure begin at temperatures above 300 • C [15] which is known to be exceeded during nanocrystallization [4,8]. Therefore, a high rate of hydrogen outburst can be expected from the structure during electroforming.…”

“…Simply electroforming of hydrogenated amorphous Si (a-Si:H) based structures can be described as the rapid crystallization induced by Joule heating under the application of electric field [1]. Electroforming of amorphous silicon based p-i-n diodes was observed by various groups in various structures [2][3][4]. Kocka's group found that their homojunction p-i-n diode was electroformed under high electric field and the diode started to exhibit strong electroluminescence (EL) in the near infrared and visible regions [2,5,6].…”

Transport and luminescence phenomena in electroformed silicon nitride-based light emitting diode

“…Keeping the bias stress on, the electroformed region laterally propagates until the accompanying bright light emission spreads over the whole diode surface. The propagation has been demonstrated by real-time photography in a recent work [18]. The time duration until this irreversible process is completed depends on the magnitude of the applied voltage: it takes almost 1 h under 9 V, while the diode is electroformed instantly (in the scale of seconds) under a calibrated voltage of 14 V. Since the thickness of the intrinsic layer of the pin diode at hand is small when compared to those of n + nc-Si:H and p + nc-Si:H films, the XRD and micro-Raman signals, which reveal the crystalline volume fraction, are not sufficient to discriminate the nanocrystallinity contribution from the intrinsic layer quantitatively.…”

“…In parallel, the low field current density (J ) increased several orders of magnitude together with enhanced EL [15]. Recently, Cabarrocas's group [16,17] and Anutgan et al [18,19] reported similar results in their electroformed hydrogenated polymorphous silicon carbide and hydrogentated amorphous silicon nitride (a-SiN x :H) pin diodes, respectively. Both groups photographed the accompanying bright visible light emitted uniformly from the whole diode area, easily perceivable by the naked eye in ordinary room conditions.…”