Investigation of metastability and instability effects on the minority carrier transport properties of microcrystalline silicon thin films by using the steady-state photocarrier grating technique

Abstract

Metastability effects in hydrogenated microcrystalline silicon thin films due to air, high purity nitrogen, helium, argon, and oxygen were investigated using temperature-dependent dark conductivity, photoconductivity, and steady-state photocarrier grating methods. It was found that short-term air, nitrogen, and inert gases caused a small reversible increase of σDark and σphoto within a factor of two, but they did not affect the minority carrier μτ-products significantly. These changes are partially reduced by vacuum treatment and completely reduced after heat treatment at 430 K. However, oxygen gas treatment at 80 °C resulted in more than an order of magnitude increase in both σDark and σphoto and an increase in the diffusion length, LD, by 50% from that of the annealed-state value in highly crystalline samples, while no significant metastability is detected in amorphous and low crystalline silicon thin films. A following heat treatment partially recovers both σDark and σphoto to their annealed-state values, while LD decreases only slightly. Such increase in the LD values could be due to a decrease in the density of recombination centers for holes below the Fermi level, which may be related to passivation of defects by oxygen on the surface of crystalline grains.

Effect of Pressure on Bonding Environment and Carrier Transport of a-Si:H Thin Films Deposited Using 27.12 MHz Assisted PECVD Process

“…Figure 6 depicts the Balberg plots of the deposited film at various process pressures and estimated values of L amb and μτ are shown in Table 2. The evaluation of L amb is difficult for films deposited at 0.03 Torr pressure due to the films having very low photosensitivity [27]. The diffusion length is constrained by the mobility (μ) and the recombination time (τ ) of the minority carriers and can be found using the relation…”

Silisyum İnce Filmlerde Taban Malzemelerin Elektronik Kusurlar Üzerine Etkisinin Belirlenmesi

“…Buna karşın yapısında nano ya da mikro kristal yapılar barındıran ve belirli bir ~%10'in üzerinde kristal hacmine sahip silisyum ince filmler atmosferik koşullardan etkilenmekte ve elektronik bozunma yaşamaktadır. [4, 6,13,14,[16][17][18][19][20][21]. Nano ya da mikro kristal silisyumlarda oluşan bu elektronik bozunmalar tamamen geri dönüşümlü olabildiği gibi kısmi ya da tamamen geri dönüşümsüz etkiler de oluşturduğu literatüre rapor edilmiştir [6,13,14,19,20,22,[26][27][28][29].…”

“…[4, 6,13,14,[16][17][18][19][20][21]. Nano ya da mikro kristal silisyumlarda oluşan bu elektronik bozunmalar tamamen geri dönüşümlü olabildiği gibi kısmi ya da tamamen geri dönüşümsüz etkiler de oluşturduğu literatüre rapor edilmiştir [6,13,14,19,20,22,[26][27][28][29].…”