Band gap narrowing and radiative efficiency of silicon doped GaN

Abstract

Radiative efficiency, band gap narrowing, and band filling are studied in Si-doped GaN films as a function of carrier concentration ͑n͒, using room and low temperature cathodoluminescence ͑CL͒. Using the Kane model, a band gap narrowing ⌬E g of −͑3.6Ϯ 0.6͒ ϫ 10 −8 and −͑2.6Ϯ 0.6͒ ϫ 10 −8 n 1/3 eV n 1/3 is obtained for epitaxially strained and relaxed material, respectively. Band-edge CL time response and absolute external photon yield are measured. The internal radiation efficiency is deduced. Its monotonic increase as n increases is explained by the increase in the spontaneous radiative rate with a radiative free carrier band-to-band recombination coefficient B = ͑1.2Ϯ 0.3͒ ϫ 10 −11 cm 3 s −1 .

Cathodoluminescence of epitaxial GaN and ZnO thin films for scintillator applications

“…Spectra are dominated by the UV band-edge (BE) emission, which peaks between 3.395 and 3.435 eV as function of n [18,29], and are further characterized by a broad, defect-related yellow band (YB) peaking invariably around 2.4 eV [30]. In order to obtain stable spectra independent from the CL excitation conditions [20], a high electron-beam current of I b ¼ 42 nA was chosen, saturating the YB.…”

“…Even though recent branches of research on ZnO focus on the realization of photonic devices as well [9,10], scintillation remains one of its primary applications [11,12]. However, detector and scintillator applications based on group III-nitrides are emerging as subjects of dedicated studies too [13][14][15][16], since GaN has a radiation hardness [17] and luminescence time response [18] comparable to ZnO [4,11,12]. Determinations of absolute cathodoluminescence (CL) efficiencies and of radiative constants of GaN and of ZnO grown by metalorganic chemical vapor deposition (MOCVD) remain extremely scarce, even though micro-CL has matured to become a standard tool [19][20][21][22][23].…”

Effect of silicon and oxygen doping on donor bound excitons in bulk GaN

“…The shift of the PL peak to lower energies becomes even more pronounced in highly doped GaN layers; 20 however, for carrier concentrations above the Mott density, the Burstein-Moss shift of the absorption edge to the higher energies has to be taken into account. 21,22 Since we study here relaxed bulk HVPE GaN we can likely neglect the strain effect on the PL peak position observed in both undoped and Si-doped samples. 23,24 Taking into account the large influence of doping on the position of the DBE PL line, we have examined the Nonradiative recombination channels become significant at elevated temperatures since they are typically activated according to τ nr = A exp(−E a /kT).…”

Photoreflectance investigation of band gap renormalization and the Burstein–Moss effect in Si doped GaN grown by MOVPE

“…Further improvements in high performance of GaN-based devices call hence for an accurate and systematic understanding of basic physical modification undergone by the material due to doping. In heavily doped semiconductor, one of the most important material parameter, namely the fundamental band gap, is frequently affected by high electron concentration as a result of a two competing effects [4][5][6][7][8][9][10][11][12]. First, the well-known Burstein-Moss (BM) band-filling effect, which shifts the absorption onset to higher energies with increasing carrier concentration [4][5][6][7][8][9][10][11][12][13][14].…”

“…In heavily doped semiconductor, one of the most important material parameter, namely the fundamental band gap, is frequently affected by high electron concentration as a result of a two competing effects [4][5][6][7][8][9][10][11][12]. First, the well-known Burstein-Moss (BM) band-filling effect, which shifts the absorption onset to higher energies with increasing carrier concentration [4][5][6][7][8][9][10][11][12][13][14]. The second phenomenon, called band gap renormalization (BGR), decreases the fundamental band gap energy with increasing carrier density due to many-body interactions [4][5][6][7][8][9][10][11][12]15].…”